KOSPI200 및 KOSDAQ150 지수 종목 변경을 활용한 공매도 효과 분석*

Analysis of Short-selling Effects Using KOSPI200 and KOSDAQ150 Indexing*

Article information

Korean J Financ Stud. 2024;53(4):393-420
Publication date (electronic) : 2024 August 31
doi : https://doi.org/10.26845/KJFS.2024.08.53.4.393
김호현, 김형준,
Assistant Professor, Handong Global University
(한동대학교 조교수)
Assistant Professor, Dongguk University
(동국대학교 조교수)
** 연락담당 저자. 주소: 서울 중구 필동로1길 30 동국대학교 경영대학 경영학과; E-mail: creatingnews@dongguk.edu; Tel: 02-2260-3502
** Corresponding Author, Address: Department of Business Administration, Dongguk Business School, Dongguk University, 30, Pildong-ro 1-gil, Jung-gu, Seoul, Republic of Korea; E-mail: creatingnews@dongguk.edu; Tel: +82-2-2260-3502
*본 논문은 한국연구재단의 지원을 받아 수행됨 (NRF-2023S1A5A8081512)*This work was supported by the Ministry of Education of the Republic of Korea and National Research Foundation of Korea (NRF-2023S1A5A8081512)
Received 2024 May 20; Revised 2024 July 23; Accepted 2024 July 25.

Abstract

금융위기 기간동안 정책입안자들은 시장의 안정을 위해 공매도 금지를 주장하곤 한다. 코로나19 팬데믹에 대응하기 위해 한국 정부는 2020년 주식시장내 공매도를 전면 금지하였고, 2021년부터 KOSPI200과 KOSDAQ150 지수에 속한 주식에 대해서만 부분적으로 공매도를 허용하였다. 이러한 한국의 특수한 공매도 정책은 두 지수가 최신화될 때, 새로 편입/편출되는 주식에 대해서 외생적으로 공매도를 허용/금지하게 만든다. 본 연구는 이를 준자연실험으로써 활용하여 공매도 허용/금지의 효과를 실증분석하고자 한다. 분석결과, 공매도 허용은 주식가격 효율성에 긍정적인 영향을 준 것으로 나타난다. 반면, 공매도 허용/금지는 주가수익률과 주가변동성에 지대한 영향을 미치지 않았다. 본 연구는 공매도의 긍정적 역할을 지지하는 실증적 증거를 제시함으로써 공매도에 관련된 정책적 시사점을 제공한다.

Trans Abstract

Financial regulators often react to crises by restricting short-selling to stabilize the stock market. In response to the COVID-19 pandemic, the Korean government banned short-selling in 2020. Since 2021, it has allowed partial resumption only for stocks indexed in KOSPI200 and KOSDAQ150. This unique short-selling regime in Korea makes newly indexed or excluded stocks experience exogenous variations in their short-selling availability when the constituents of the two indices are updated. Using this quasi-natural experimental setting, we examine the impact of short-selling permission and ban. The results show that short-selling permission enhances stocks’ price efficiencies while short-selling permission and ban do not strongly influence stock return or volatility. Overall, this paper provides empirical evidence supporting the positive role of short-selling, further casting doubts on the reasons behind banning short-selling.

Keywords:

1. Introduction

“Banning short-sellinginterferes with price formation, thereby increasing uncertainty. That can only artificially amplify volatility and probability of default, the opposite effect to that claimed, and hampers the ability of markets to serve the real economy. It is not – and never has been – true that bans have any other, positive effect on market activity or price levels.”

- 30 March 2020, The World Federation of Exchanges (WFE)1)

WFE criticizes recent bans on short-selling against the stock market crash due to the COVID-19 pandemic.2), The European Union and a number of emerging countries, such as South Korea, Spain, and France decided to engage in short-selling to protect their capital market. In contrast, the U.S., U.K., and Japan had refused to engage in short-selling in their stock market, as they believe that “there is no evidence that it is a driver of market routs.”3)

Short-selling restrictions havebeen extensively studied in the finance literature, typically since the 2008 financial crisis, however, academicand practical evidence on the effect of short-selling is still controversial (e.g., Jiang et al., 2022). On the one hand, short-sellers who might be sophisticated investors canplay an important and positive role in price efficiency. On the other hand, short-selling activities may manipulate stock prices and destabilize the market, and thus, regulators react to the crisis period by restricting short-selling.

Nevertheless, empirical specification for examiningthe impact of short-selling is challenging because of endogeneity concerns, such as selection bias and reverse causality. Addressing such concerns is difficult without exogenous change in short-selling activities. Thus, the literature has attempted to constructa quasi-natural experiment using the regulatory change on short-selling. For instance, Beber and Pagano (2013) focus on the regulatory interventions imposing bans on short-selling around the world during the 2008 financial crisis. The U.S. short-selling Regulation SHO also can be viewed as an exogenous shock, and thus, allows conducting empirical design in prior studies (Deng et al., 2020; Fang et al., 2016; Grullon et al., 2015; Li and Zhang, 2015).

With this regard, the current Korean stock market provides an ideal setting to overcome endogeneity issues because of its unique regulations on short-selling from 2020 to 2021. In March 2020, short-selling activities for all the listed stocks on the Korea Exchange (KRX)4), were suspended due to the COVID-19 shock. After about 14-months later, since May 2021, short-selling activities have been allowed but only for stocks that are components of the following two representative indices in the KRX: KOSPI200 and KOSDAQ150.5), Therefore, when the constituents of these indices are updated, newly indexed or excluded stocks in 2021 have experienced exogenous shocks in their short-selling availability. By comparing impacts of the index addition or out both in 2020 and 2021, we attempt to examine the relatively pure impacts of short-selling activities in Korea. More specifically, in order to assume that entering in or removing from KOSPI200 and KOSDAQ150 constituents is randomly determined, which is a key condition of a quasi-experimental setting, we restrict our sample into similar stocks in market size and trading volume.In other words, we set the control group as such similar stocks but do not experience inclusion or exclusion at the date of KOSPI200 and KOSDAQ150 constituents change, while the treatment group as the stocks that have entered in or removed from the indices. As a result, the treatment and control groups are basically similar, but after the date of indices’constituents change, only the treated stocks are suddenly available/forbidden for short-selling in the market because of their affiliation changes. Note that although a number of prior studies have investigated short-selling in Korea (e.g., Jung et al., 2013; Lee and Wang, 2022; Wang, 2023), our study is the first attempt to employ this quasi-experimental regulatoryto understand impacts of short-selling permission or ban.

Using this quasi-experimental setting due to the unique short-selling regime change in the Korean stock market, we first confirm that stocks belonging to KOSPI200 or KOSDAQ150 index in 2021 have experienced a significant increase in their short-selling volume, supporting the validity of our empirical design. For instance, if short-sellers in the Korean stock market are not interested at all to short newly indexed stocks, our empirical strategy could be meaningless; however, we find that such newly indexed stocks have significant short-selling volume immediately after their index inclusion.In addition, short-selling volume for stocks that are excluded from KOSPI200 or KOSDAQ150 index after the index update date immediately drop.

Most importantly, we find that short-selling permission in the Korean stock market enhances the affected stocks’ price efficiencies, andthus, it can contribute to improving market efficiency. This finding is also consistent with the view in recent studies that suggest a prominent role of short-selling in price discovery (e.g., Bushman and Pinto, 2024; Luu et al., 2023). Our results further imply that short-selling permission appears to be related to stock price appreciation. However, we find no evidence short-selling permission/ban strongly affects stock volatility, which is contrary to the general argument on short-selling in the Korean stock market.

We ensure that this paper provides practical and policy implications. According to our empirical evidence, short-selling permission appears to improve price efficiency, thereby contributing to the KRX. It suggests that short-sellers (using their information) play an important role in price discovery to some extent. Moreover, our paper shows no evidence that short-selling activities are strictly detrimental to stock returns or volatilities. Although our finding (at least partially) supports the positive side of short-selling in the Korean stock market, we note that its generalization to smaller stocks should be carefully studied further as we fail to find the consistency of evidence with the KOSDAQ-only sample. This suggest that stocks with low liquidity might have different outcomes with short-selling permission/ban.

The remainder of this paper is organized as follows. Section 2 reviews therelated literature on short-selling. Section 3 describes the unique institutional background about short-selling regime in the Korean stock market and our empirical specification. Section 4 presents the empirical results. Section 5 concludes the paper.

2. Related literature

Short-selling is a well-known trading strategy, that is “selling high and buying low.” Starting from early studies that theoretically compare the cost and risks ofshort-selling (e.g. Diamond and Verrecchia, 1987; Miller, 1977), the related literature generallyposits that short sellers are sophisticated or informed traders in the market as they will short stock only if they believe that their targeting stocks will compensate for additional costs and risks. Such bearing costs and risks in short-selling are, for example, unlimited loss with stock price incline, which is also recently highlighted by the GameStop episode (Atmaz et al., 2024), and restrictions on access to proceeds and some legal constraints (Diamond and Verrecchia, 1987).

Miller (1977) argues that overpriced stocks exist in the market if there is disagreement about these values among investors. In addition, if the market restricts pessimistic investors who might want to short such overpriced stocks (which could be viewed as short-selling bans), this overpricing phenomenon is more likely to occur.For instance, if short sellers are allowed to short an overpriced stock before its bad earnings announcement, and they are rational and informed investors, they can cool down such an overpriced stock’s price even before its earnings announcement, implying a positive role in price discovery of short sellers.

However, a stream of research argues that short-selling is detrimental in society, as short sellers are indeed uninformed but just predatory traders (in general, speculative institutional investors). As a result, short-selling per se is likely to be associated with stock price manipulation, increase in market volatility, and signaling of selling pressure that makes profits for predatory short sellers (Allen and Gale, 1992; Brunnermeier and Oehmke, 2014).

Given the nature of the short-selling strategy, the endogeneity threat is critical in the short-selling literature, as highlighted by Jiang et al. (2022), which is a review paper on short-selling. For instance, it is difficult to argue whether a stock’s short-selling pressure causes its subsequent price drop or short-sellers indeed target such a stock that will drop in the near future. Therefore, a large body of empirical studies attempts to address endogeneity concerns by using exogenous change in short-selling activities.

As a result, regulations on short-selling have been extensively studied in the finance literature, particularly exploiting the 2008 financial crisis in which many financial regulators imposed a ban onshort-selling to reduce volatility and to stem the market crash. However, the empirical evidence is mixed or even contradicts the reason for banning short-selling.

Boulton and Braga-Alves (2010) find that short-selling bans, in fact, do not reduce market volatility on average exploiting the US Securities and Exchange Commission’s (SEC) temporary restrictions on naked short sales of the stocks of 19 financial firms in July 2008. Saffi and Sigurdsson (2011)use the global sample from 2005 to 2008, and they find that short-selling restrictions are harmful to market efficiency, and the subsequent relaxing of such restrictions does not induce volatility or the extreme stock price drop. Bris et al. (2007) also highlight the positive side of removing short-sale restrictions, using regulatory intervention on whether short-selling is prohibited or practiced in 46 countries. Chang et al. (2007) who examine the Hong Kong sample find that short-selling bans on individual stocks tend to cause overvaluation, in line with the argument of Miller (1977). More recently, Luu et al. (2023) examine the effect of short-selling in the US market after the COVID-19 pandemic. The authors find that, during the COVID-19 shock in the stock market, short-selling activities are only concentrated on overpriced stocks, suggesting that short-selling plays a role in improving price discoveries insteadof triggering stock market crashes.

In terms of the Korean stock market, several papers have examined the effect of short-selling in the stock market (Jung et al., 2013; Chung and Wang, 2020; Lee and Wang, 2019, 2022; Wang, 2023; Wang et al., 2017; Wang and Lee, 2015). Notably, most research focusing on the Korean sample also exploits the Korean government’s intervention in October 2008, which was temporary bans for all forms of short-selling due to the financial crisis. Jung et al. (2013) suggest that short-selling (by individual investors) contributes to price efficiency in the stock market. Wang and Lee (2015) find that short-selling in the Korean stock market is mainly driven by foreign investors, and their short-selling does not induce market volatility. More recently, Wang (2023) examines the predictability of short-selling on future returns in the Korean stocks. Further, the author finds that short-selling is more concentrated for larger firms with better credit grades, in contrast to the US market, and short-selling has a predictivepower on stock returns only for such larger firms.

It is worth to note that, to the best of our knowledge, there is no research yet exploiting short-selling regime changes in the Korean stock market against the COVID-19 pandemic, although there are several prior studies on short-selling using the Korean sample. We will discuss our empirical strategy that exploits the unique institutional setting in Korea around the COVID-19 pandemic in the next section.

3. Institutional background and empirical identification

In March 2020, the Korean government agency, the Financial Services Commission (FSC) decides to engage in short-selling activities in the Korean market. We collect related announcements from press releases of the FSC, summarized in Panel A of Table 1. Specifically, the FSC warns about the worldwide spread of COVID-19 (also, in Korea) and its negative shock on the stock market as well as significant rocketing volatility and short-selling volume. Therefore, they decide to impose a ban on short-selling for the 6-months period as a stock market stabilization instrument. This short-selling ban, however, has continued exceptionally long for about 14-months from March 2020 in Korea. After that, the FSC decided to resume short-selling activities in the KRX, but more importantly, allowing only for KOSPI200 and KOSDAQ150-indexed stocks.

Key information for empirical specification

Note. This table illustrates key information for our empirical identification. Panel A summarizes the Korean government’s intervention on short-selling in KRX against the COVID-19 pandemic shock from early 2020 to 2021. Panel B summarizes the regular updates in 2020 and 2021 for KOSPI200 and KOSDAQ150. For these two representative indices, KRX regularly announces update twice in a year (every June and December). Panel C shows the treatment and control groups in our empirical specification around the four regular updates of the indices in 2020 and 2021. In Panel C, Index_in (Index_out) equals to one for stocks that are newly indexed (excluded) in terms of KOSPI200 and KOSDAQ150, and zero for the control group. We define the control group as ten (five)nearest neighbors with each of the treated stocks by performing the propensity score matching technique among stocks that have not experienced changesin their affiliations for KOSPI200 or KOSDAQ150 index at the dates of the four regular updates of the indices, denoted by Larger (Smaller) control group.

Panel A: Short-selling related announcements in 2020 and 2021 by the Korean government

This paper focuses on the date of KOSPI200 and KOSDAQ150 constituents change in 2021 as the index-included/excluded firms suddenly experience short-selling permission/ban. Note that constituents of the index are updated in June and December every year in a regular manner (hereafter, the regular update), as summarized in Panel B of Table 1. Nevertheless, still there is a potential concern because the index’s regular update might be related to money flow from passive funds in financial institutions. For instance, some passive funds may include only stocks belonging to the KOSPI200 or KOSDAQ150 indices, thus stocks that are indexed or excluded may experience exceptional changes in demand from the passive funds. To address this concern, our empirical strategy is to use the same regular update events that occurred in 2020 as a base.

The only difference inwhether a stock belongs to KOSPI200 or KOSDAQ150 index between 2020 and 2021 is short-selling availability. Thus, most importantly, we can estimate the impact of short-selling permission/ban by comparing the index’s regular update (i.e., the index addition/out) in 2020 and 2021.6) Assuming that entering in or removing from KOSPI200 and KOSDAQ150 constituents among similar stocks around the threshold of such indices is (almost) random, our empirical strategy can be viewed as a quasi-natural experiment. Overall, we implement the following difference-in- difference (DID) specification:

where the dependent variable is a target variable of interest, such as short-selling volume and price efficiency measures. Index_changeit is an indicator that equals one for the treatment group: stocks changing their affiliation at the date of the index’s regular update, and more specifically, Index_in and Index_out, and zero for the control group: stocks that are around KOSPI200 and KOSDAQ150 indices’ threshold but are unchanged in terms of their affiliations at the index’s regular update. We describe available observations for the treatment and control groups in Panel C of Table 1. More specifically, to construct the control group, we first identify stocks that have not experienced changes in their affiliations for KOSPI200 or KOSDAQ150 index. Among these stocks, we then perform the propensity score matching technique to find ten or five nearest neighbors with each of the treated stocks (hereafter, denoted by Larger or Smaller control group, respectively).7) The indicator Y2021 is the post variable of the unique short-selling regime in the Korean stock market, which equals to one for observations in 2021 and zero for ones in 2020.

(1)Yit=β1Index_changeit+β2Y2021+β3(Index_changeit×Y2021)+ΓControl variablesit+δj+εit,

It is noteworthy that, since we include observations at the regular update events in 2020, β1 can represent the impact of the index addition/out in 2020, such as money flow from passive funds. The coefficient of Y2021 (i.e., β2) is econometrically identical to year fixed effect, thus, our empirical tables do not mention year fixed effect. Most importantly, our main DID estimator β3 indicates difference in the effect of the index addition/out between 2020 and 2021, thereby referring to the pure impact of short-selling permission/ban.

Furthermore, we control for the stock’s market capitalization and trading volume. To control for market-specific and industry-specific effects, we also include an indicator that equals one for stocks listed on KOSPI and zero for KOSDAQ, and the industry fixed effects (δj) based on 17 sections of the Korean Standard Industrial Classification (KSIC).

We manually collect data on KOSPI200 and KOSDAQ150 constituent changes from the KRX announcement,8), and provide the list of stocks that experienced index-in and index-out (i.e., the treatment group) from 2020 to 2021 in Appendix A. We also obtain stock price and trading data from FN Dataguide. Then, we construct a cross-sectional sample around the regular update in June and December 2020 and 2021 (i.e., four events). All the continuous variables are winsorized at the 1st and 99th levels to reduce the effect of outliers. Panels A and B of Table 2 show the detailed definitions of variables and the descriptive statistics, respectively.

Sample summary

Note. This table illustrates definitions of the variables and summary statistics in Panels A and B, respectively. We winsorize all continuous variables at 1st and 99th percentiles to remove the influence of outliers. Panel C reports the mean difference in stocks’ market capitalization and trading volume between the treatment (Index_in = 1 or Index_out = 1) and the corresponding control groups (Larger and Smaller control group).

Panel A: Definitions of variables

4. Empirical analysis

4.1. Validity test

Before we investigate the impact of short-selling permission/ban, it is necessary to check the validity of our empirical specification. In Panel C of Table 2, we first examine whether our two main control variables (i.e., the stock’s market capitalization and trading volume) significantly differ by the treatment and control groups.9) The first and second rows in Panel C focus on the samples of Index_in and Index_out, and the last two columns report the t-statistics for the mean difference between the treatment group versus the Larger or Smaller control group, respectively. Both columns show that the t-statistics for the mean difference are sufficiently small. Thus, the results of Panel C suggest that the treatment and control groups are basically similar in our sample construction, further supporting the underlying assumption of our empirical strategy.

Next, we examine whether short-selling activities of stocks that have entered in (Index_in) or removed from (Index_out) KOSPI200 and KOSDAQ150 indices are indeed affected, compared to the control group. For instance, if short-selling volume per se of the treated stocks (i.e., newly-entered stocks in KOSPI200 and KOSDAQ150 indices) is unaffected, it may indicate that short-sellers are, in fact, not interested in the treated stocks that are close to around those indices’ threshold; if so, our empirical specification could be invalid.

Table 3 presents the results of this validity test.Odd-numbered columns indicate Larger control group, whereas even-numbered columns use a more restrictive criterion, Smaller control group, for selecting the control group as described in the previous section. Following the literature on short-selling (Diether et al., 2009; Lee and Wang, 2019), we calculate relative short-selling as the trading volume of short-selling divided by the total trading volume, and we take its difference between those for1-, 2-, and 3-months (i.e., 20-, 40-, 60-trading-days) before and after the index’s regular update. As we expect, the interaction terms between Index_in (Index_out) and Y2021 show positive (negative) estimates, whereas both the standalone estimates of Index_in and Index_out are insignificant in Table 3. These results imply that belonging to KOSPI200 or KOSDAQ150 index in 2021 is significantly associated with short-selling activities, supporting that our empirical design can be a quasi-natural experiment.

Effects of short-selling permission/ban on short-selling volume

Note. This table reports the results of validity tests where the dependent variable is short-selling volume changes, the difference in short-selling relative volume between before and after the index updates (based on 20, 40, and 60 trading days). Models (1)-(6) and (7)-(12) examine the impact of short-selling permission and ban, respectively. Definitions of the variables are described in Panel A of Table 2. Parentheses report t-statistics based on standard errors adjusted for heteroscedasticity. *, **, and *** indicate significance at the 10%, 5%, and 1% levels, respectively.

4.2. Main results: Impact of short-selling permission/ban

Table 4 analyzes the impact of short-selling permission/ban on price efficiency. In particular, we adopt two measures of price efficiency proposed by Hou and Moskowitz (2005), also referred to as price delay in the literature (e.g., Saffi and Sigurdsson, 2011). Note that a lower value of price delay indicates a higher price efficiency, and thus, a more efficient price discovery in the stock market. In Table 4, the dependent variable is the difference in between price delay calculated by 3-months (i.e., 60-trading-days) before and after the index’s regular update. In columns (1)–(4), β3 (i.e., the interaction terms between Index_in and Y2021) is negatively estimated on price delay measures at least at the 10% significance level, suggesting that short-selling permission appears to improve the affected stocks’ price efficiencies. We find no evidence that short-selling ban significantly influences price efficiency in our empirical design (columns (5)–(8)). The results in Table 4 are generally consistent with the prior literature revealing the positive impact of short-selling on price efficiency (Beber and Pagano, 2013; Saffi and Sigurdsson, 2011).

Effects of short-selling permission/ban on price efficiency

Note. This table reports the main results where the dependent variable is changes in price efficiency measures. We calculate Hou and Moskowitz’s (2005) measures, Price delay 1 or 2, for each stock and take its difference between 60 trading days before and after the index update. Models (1)-(4)and (5)-(8) examine the impact of short-selling permission and ban, respectively. Definitions of the variables are described in Panel A of Table 2. Parentheses report t-statistics based on standard errors adjusted for heteroscedasticity. *, **, and *** indicate significance at the 10%, 5%, and 1% levels, respectively.

Next, we examine whether the affected stocks by short-selling permission/ban exhibit different patterns of stock returns or volatilities. Market participants in the Korean stock market (typically, retail investors) often argue that short-selling should be banned because, for example, foreign investors intensively short-sell Korean stocks and take earnings out of the Korean stock market. It is not difficult to see news suggesting that short-selling is one significant factor of market meltdown.

Table 5 presents the results where we focus on stock returns for 1-, 2-, and 3-months (i.e., 20-, 40-, 60-trading-days) after the index’s regular update. In columns (1)–(6), the treatment group in 2020 (i.e., Index_in) is likely to have negative returns compared to the control group. However, β3 (i.e., Index_in × Y2021) in these columns generally have significantly positive coefficients; we cautiously interpret that this could be due to the improved price discovery (as shown in Table 4), but it needs to be studied further. In addition, β3 for Index_out shows the opposite direction in columns (7)–(12), although the statistical significance levels are relatively weak.

Effects of short-selling permission/ban on stock returns

Note. This table reports the main results where the dependent variable is stock returns for the next 20, 40, and 60 trading days after the index updates. Models (1)-(6) and (7)-(12) examine the impact of short-selling permission and ban, respectively. Definitions of the variables are described in Panel A of Table 2. Parentheses report t-statistics based on standard errors adjusted for heteroscedasticity. *, **, and *** indicate significance at the 10%, 5%, and 1% levels, respectively.

We conclude that the results of Table 5 contradict the general belief about short-selling in the Korean stock market. On the one hand, at the very least, short-selling permission is not destroying stock returns on average; instead, we find that it could be positively related to stock returns. On the other hand, there is no evidence that short-selling ban could be helpful to protect stock returns. Our interpretations are consistent with Saffi and Sigurdsson’s (2011) argument that relaxing short-selling constraints does not lead to negative stock returns.

Table 6 examines the impact of short-selling permission/ban on stock volatility. To measure the change in stock volatility around the index’s regular update, we calculate a variance of daily stock returns during 1-, 2-, and 3-months (i.e., 20-, 40-, 60-trading-days) before and after the index’s regular update. We take its difference (between before and after value) and standardize by its before value. Here, we find that the treated stock’s volatility by short-selling permission does not show significant changes on average during all the three periods (see, β3 in columns (1)–(6)). Index_out × Y2021 also shows insignificant coefficients in columns (7)-(12), concluding that short-selling ban also has no significant impact on stock volatility.

Effects of short-selling permission/ban on stock volatility

Note. This table reports the main results where the dependent variable is changes in stock volatility. We calculate a variance of daily stock returns for each stock and take its ratio of the difference between before and after the index updates (based on 20, 40, and 60 trading days) to the before value. Models (1)-(6) and (7)-(12) examine the impact of short-selling permission and ban, respectively. Definitions of the variables are described in Panel A of Table 2. Parentheses report t-statistics based on standard errorsadjusted for heteroscedasticity. *, **, and *** indicate significance at the 10%, 5%, and 1% levels, respectively.

Taken together for Tables 5 and 6, we repeatedly note that our empirical evidence is against the general belief about short-selling in the Korean stock market. For instance, if short-selling activities are associated with (inappropriate) selling pressure, and thus, negatively influence stock price, short-selling permission/ban could be bad/good news for shareholders. However, we rather find the opposite results which are weakly positive (negative or insignificant) stock returns even after short-selling permission (ban). The results on stock volatility, regardless of whether the event is Index_in or Index_out, are also not strong enough to claim the detrimental role of short-sellers.Note that our results are also consistent with prior studies that suggest the absence of evidence for speculative short-sellers in the Korean stock market (Jung et al., 2013; Wang and Lee, 2015).

Notably, our empirical evidence suggests that short-selling permission in the Korean stock market improvesprice efficiency. In addition, we argue that stock returns and volatility of the treatment groups are not strongly affected compared to the control groups in our empirical setup. Thus, we argue that there is no strongevidence supporting the evil side of short-selling in the Korean stock market, such as dropping stock price, limiting market efficiency, and destabilizing market by predatory short sellers; rather, our study supports the bright side by suggesting an important role of short-selling for price efficiency and discovery (Beber and Pagano, 2013; Saffi and Sigurdsson, 2011).

4.3. Robustness tests

As robustness tests, we first exclude firms that were newly listed on the exchange within six months before the index’s regular updates. This exclusion is because the largest shareholders cannot sell their shares for six months after initial public offerings(IPOs), which might skew our analysis. We identify 22 newly listed firms around the analytic events, as reported in Appendix B. After excluding these firms from our sample, we find that the previous results in Tables 3, 4, 5, and 6 maintain similar patterns of significance (untabulated).

Second, we reperform the previous tests for the KOSPI-only or KOSDAQ-only sample. In these untabulated results, we find that the KOSPI-only sample exhibits qualitatively similar patterns likewise our reported empirical tables. However, the same tests for the KOSDAQ-only sample show insignificance in most of the key coefficients.We cautiously argue that this insignificant result could be due to the relatively large instability of the KOSDAQ market (in terms of both stock price and volatility). Thus, one might argue that the impact of short-selling permission and ban could differ in the KOSDAQ market. Since our study cannot completely resolve this point, a deeper study is necessary in the future because stocks in the KOSDAQ market could have different characteristics relative to the KOSPI market.

5. Conclusion

In November 2023, the Korean FSC again decided to suspend short-selling activities in the Korean stock market. This suspension will continue to March 2025, and until that time, the Korean government is aiming to build the system to monitor speculative short sellers. With this regard, ourpaper can provide both academic and practical implications, by attempting to employ the recent regulation changes on short-selling in the Korean stock market.

First, we suggest that the current regime in the Korean stock market can be an ideal setting to construct academic research on the impact of short-selling. More specifically, we adopt a quasi-natural experiment design using the constituents change in KOSPI200 and KOSDAQ150 indices in 2020 and 2021, aiming to overcome potential endogeneity concerns. Since endogeneity threat is critical in the short-selling literature, this novelapproach alleviates such concerns and enables us to examine thepure impact of short-selling permission/ban.

Second, our empirical analysis shows evidencethat at least some short-sellers play an important role in price discovery, rather than its detrimental role in society. In particular, short-selling permission in the Korean stock market appears to enhance the affected stocks’ price efficiencies, and thus, it can contribute to improving market efficiency. Notably, in line with our results, recent studies on short-selling also suggest the positive role of short-selling (e.g., Bushman and Pinto, 2024; Luu et al., 2023).

Third, there is no clear evidence that short-sellers are predatory traders on average in Korea. In our empirical results, we never findthat short-selling activities are harmful to the stock market, neither from the perspective of stock returns nor volatilities. This result is also consistent with prior studies, which strongly suggestthe absence of evidence for speculative short-sellers in the Korean stock market (Jung et al., 2013; Wang and Lee, 2015).

Recently, in June 2024, Morgan Stanley Capital International (MSCI) announced that South Korea failed to include in its index of the developed market.10) In particular, MSCI pointed out that the Korean government’s intervention in short-selling ban in November last year is not desirable. This MSCI view is in linewith one from the WFE statement in March 2020 (as illustrated in the Introduction). Consistent with these views, our paper concludes that banning short-selling might not be helpful for stabilizing the market, further casting doubts on the reason for banning short-selling. Yet, some future studies are required to check whether short-selling rules towards smaller stocks also show the same pattern of empirical evidence in this paper.

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Appendix

Stocks in the treatment group (in Korean)

Stocks those are newly-listed within 6 months at the index update date (in Korean)

Notes

2)

In addition, WFE mentioned that short-selling bans prevent market participants from trading as effectively as possible, thereby making price information less accurate.

3)

Reuter also pointed out the regulatory intervention on short-selling by citing the statement of WFE. See, https://www.reuters.com/article/business/short-selling-bans-not-useful-stock-exchanges-federation-idUSKBN21H0VJ/.

4)

The KRX comprises two listing venues: the Korea Composite Stock Price Index (KOSPI) and the Korean Securities Dealers Automated Quotation (KOSDAQ).

5)

See, for more detailed description, the announcement of the Korean government agency, the Financial Services Commission (FSC), on 3 February at their website: [FSC Announces Decision on Short-selling Ban] (https://www.fsc.go.kr/eng/pr010101/75291?srchCtgry=&curPage=&srchKey=sj&srchText=&srchBeginDt=2021-02-01&srchEndDt=2021-02-04).

6)

See, Appendix A for the list of stocks that experienced index-in and index-out (i.e., the treatment group) from 2020 to 2021.

7)

During matching to obtain the nearest neighbors of each treated stocks, we allow the replacement for better matching quality, so different treated stocks may share the same matched control stocks. Thus, it is natural that size of the Larger (or Smaller) control group could be less than 10 (or 5) times the size of the treatment group.

8)

See, for more detailed description, the official website of KRX (http://data.krx.co.kr).

9)

We thank an anonymous reviewer for suggesting this mean difference test between the treatment and control groups.

10)

South Korea is currently classified as the emerging market index of MSCI. For more detail, see, https://www.hankyung.com/article/2024062135581

Article information Continued

<Table 1>

Key information for empirical specification

Note. This table illustrates key information for our empirical identification. Panel A summarizes the Korean government’s intervention on short-selling in KRX against the COVID-19 pandemic shock from early 2020 to 2021. Panel B summarizes the regular updates in 2020 and 2021 for KOSPI200 and KOSDAQ150. For these two representative indices, KRX regularly announces update twice in a year (every June and December). Panel C shows the treatment and control groups in our empirical specification around the four regular updates of the indices in 2020 and 2021. In Panel C, Index_in (Index_out) equals to one for stocks that are newly indexed (excluded) in terms of KOSPI200 and KOSDAQ150, and zero for the control group. We define the control group as ten (five)nearest neighbors with each of the treated stocks by performing the propensity score matching technique among stocks that have not experienced changesin their affiliations for KOSPI200 or KOSDAQ150 index at the dates of the four regular updates of the indices, denoted by Larger (Smaller) control group.

Panel A: Short-selling related announcements in 2020 and 2021 by the Korean government

Dates Information (Source: Press Releases of the Financial Services Commission (FSC); https://www.fsc.go.kr/eng/pr010101)
March 13, 2020 [Government Unveils Stock Market Stabilization Measures] The FSC announces that they impose a ban on stock short-selling for a period of six months from March 16 to September 15.
March 16, 2020 Short-selling activities are suspended for all stocks in the Korea Exchange (KRX).
August 27, 2020 [Temporary Ban on Short Sale to be Extended for Six Months] The FSC announces that they extend the temporary ban on stock short sale for six months from September 16, 2020, to March 15, 2021, given market volatility amid concerns over a resurgence in COVID-19 cases.
February 3, 2021 [FSC Announces Decision on Short-selling Ban] The FSC announces the decision to extend the short-selling ban until May 2, 2021, and to allow a partial resumption of short-selling from May 3, 2021 on KOSPI 200 and KOSDAQ 150 stocks. Because KOSPI 200 and KOSDAQ 150 stocks are familiarto domestic and foreign investors. These indices also have high utilization, such as linked trading between the derivatives market and the stock market. Due to large market capitalization and sufficiently high liquidity, short selling is expected to only have a limited effect on stock price.
May 3, 2021 Short-selling (partially) resumes only for KOSPI 200 and KOSDAQ 150 stocks.

Panel B: Regular update for the KOSPI200 and KOSDAQ150 constituents in 2020 and 2021

Dates KOSPI200 index KOSDAQ150 index Short-selling availability Note

June 12, 2020 Regular inclusion: 11 stocks Regular exclusion: 11 stocks Regular inclusion: 14 stocks Regular exclusion: 14 stocks Banned
December 11, 2020 Regular inclusion: 10 stocks Regular exclusion: 10 stocks Regular inclusion: 17 stocks Regular exclusion: 17 stocks Banned
June 11, 2021 Regular inclusion: 5 stocks Special inclusion: 1 stock Regular exclusion: 6 stocks Special exclusion: 1 stock Regular inclusion: 16 stocks Regular exclusion: 16 stocks Only allowed for the indices’ constituents Special update: “SK ie technology” is added after its IPO, and correspondingly, “HDC” is excluded.
December 10, 2021 Regular inclusion: 5 stocks Special inclusion: 1 stock Regular exclusion: 6 stocks Special exclusion: 1 stock Regular inclusion: 14 stocks Regular exclusion: 15 stocks Only allowed for the indices’ constituents Special update: “Kakaopay” is added after its IPO, and correspondingly, “LOTTE Himart” is excluded.

Panel C: Available observations for the treatment and control groups at the index’s regular update

  Treatment group Control group for Index_in (Index_in = 0) Control group for Index_out (Index_out = 0)

Index_in= 1 Index_out = 1

Dates for regular update # of stocks entering in the index # of stocks removing from the index # of matched stocks (1:10 matching with replacement; Larger control group) #of matched stocks (1:5 matching with replacement; Smaller control group) # of matched stocks (1:10 matching with replacement; Larger control group) # of matched stocks (1:5 matching with replacement; Smaller control group)
June 12, 2020 24 22 145 77 90 45
December 11, 2020 26 23 132 71 60 30
June 11, 2021 22 23 102 56 70 35
December 10, 2021 20 21 134 66 50 25

Total 92 82 513 270 270 135

<Table 2>

Sample summary

Note. This table illustrates definitions of the variables and summary statistics in Panels A and B, respectively. We winsorize all continuous variables at 1st and 99th percentiles to remove the influence of outliers. Panel C reports the mean difference in stocks’ market capitalization and trading volume between the treatment (Index_in = 1 or Index_out = 1) and the corresponding control groups (Larger and Smaller control group).

Panel A: Definitions of variables

Variable Definition
Index_in Dummy variable equals one for the treated stocks that have newly entered in KOSPI200 or KOSDAQ150 index at the index’s regular update, and zero for the control (matched) stocks in which those affiliations are not changed at the index’s regular update and satisfied the propensity score matching (the 10 or 5 nearest neighbors).
Index_out Dummy variable equals one for stocks that have been removed from KOSPI200 or KOSDAQ150 index at the index’s regular update, and zero for the control (matched) stocks in which those affiliations are not changed at the index’s regular update and satisfied the propensity score matching (the 10 or 5 nearest neighbors).
Y2021 Dummy variable equals one for the year 2021, and zero for 2020. This is the post variable for our quasi-natural experiment design as the Korean unique short-selling regime begins in May 2021.
ln(Market cap.) Natural logarithm of a stock’s market capitalization (in Korean won) at the date of the index’s regular update
ln(Trading vol.) Natural logarithm of a stock’s trading volume (in Korean won) at the date of the index’s regular update.
KOSPI Dummy variable equals one for the stock listed on the KOSPI market, and zero for the KOSDAQ market.
N(Short-selling volume divided by trading volume) Let A be an average short-selling volume divided by an average trading volume during N trading days before the index’s regular update. Let B be similarly defined during N trading days after the index’s regular update. The variable is defined as B minus A.
60d(Price delay 1) We estimate price delay by following one of the measures in Hou and Moskowitz (2005). Using weekly stock returns from 60 trading days the index’s regular update, we run the following regression model:
rit=αi+βiRmt+n=14δi(n)Rm(tn)+εit
where rt is the stock’s return at week t and Rmt is a market return at week t. We use returns of the KOSPI index or the KOSDAQ index as market returns, for KOSPI firms or KOSDAQ firms, respectively. Let R02 be the R2 from the above regression without any restrictions, and let Rδ2 =0 be the R2 from the model with restriction of δi(-n) =0for all n. Then, Price delay 1 during the period is defined as follows:
Price delay 1=1Rδ=02R02,
Note that if lagged market returns explain the stock’s current return, indicating low price efficiency, this measure has a value greater than 0. Let A be Price delay 1 measured using weekly stock returns from 60 trading days before the index’s regular update. Let B be similarly defined during 60 trading days after the index’s regular update. The variable is defined as B minus A.
60d(Pricedelay 2) We estimate price delay by following one of the measures in Hou and Moskowitz (2005). At first, we run the above regression model. Then, Price delay 2 is defined as follows:
 Price delay 2=n=14nδi(n)βi+n=14nδi(n)
This measure is developed to give more weights to influence of longer lags of market returns. Note that similar to Price delay 1, this measure also has a higher value when influence of lagged market returns is greater or price efficiency is lower. Let A be Price delay 2 measured using weekly stock returns from 60 trading days before the index’s regular update. Let B be similarly defined during 60 trading days after the index’s regular update. The variable is defined as B minus A.
Stock returns for the next N days Stock returns during the next N trading days after the date of the index’s regular update
N(Stock volatility) Let A be a variance of daily stock returns during N trading days before the index’s regular update. Let B be similarly defined during N trading days after the index’s regular update. The variable is defined as B minus A, scaled by A.

Panel B: Descriptive statistics

Variable # of obs. Mean Std. Dev. Min Max
Index_in 869 0.1081 0 1
Index_out 869 0.1116 0 1
Y2021 869 0.4672 0 1
ln(Market cap.) 859 26.5038 1.6578 22.8941 31.6641
ln(Trading vol.) 868 23.4746 1.5991 18.8119 27.2900
KOSPI 869 0.5180 0 1
20d(Short-selling volume divided by trading volume) 800 -0.0027 0.0503 -0.4660 0.4048
40d(Short-selling volume divided by trading volume) 807 0.0000 0.0667 -0.8793 0.4973
60d(Short-selling volume divided by trading volume) 812 0.0043 0.0589 -0.4637 0.8040
60d(Price delay 1) 836 0.0292 0.3251 -0.8324 0.8766
60d(Price delay 2) 844 0.0585 0.3284 -0.8291 0.8692
Stock returns for the next 20 days 852 0.0258 0.0146 -0.2950 0.9119
Stock returns for the next 40 days 857 0.0479 0.2300 -0.3920 1.2104
Stock returns for the next 60 days 853 0.0575 0.3147 -0.4698 2.6151
20d(Stock volatility) 849 0.1935 0.7481 -0.7128 5.1994
40d(Stock volatility) 855 0.1267 0.6263 -0.7922 4.2392
60d(Stock volatility) 852 0.0103 0.5280 -1.0000 4.1745

Panel C. Mean difference between the treatment and control groups

Variables Treatment group: (1) Control group t-statistics (p-value)

Larger control group: (2) Smaller control group: (3) (1) vs. (2) (1) vs. (3)

Mean Std. Err. Mean Std. Err. Mean Std. Err.

Index_in ln(Market cap.) 26.5783 0.0852 26.4215 0.0633 26.5756 0.0924 1.4760 (0.1428) 0.0207 (0.9835)
ln(Trading vol.) 24.0620 0.1214 23.8744 0.0585 23.9959 0.0808 1.3915 (0.1666) 0.4529(0.6512)

Index_out ln(Market cap.) 26.0925 0.0623 26.0838 0.0469 26.0859 0.0520 0.1110 (0.9118) 0.0812 (0.9355)
ln(Trading vol.) 22.6384 0.0898 22.5000 .0759 22.4652 0.1015 1.1756 (0.2410) 1.2768(0.2031)

<Table 3>

Effects of short-selling permission/ban on short-selling volume

Note. This table reports the results of validity tests where the dependent variable is short-selling volume changes, the difference in short-selling relative volume between before and after the index updates (based on 20, 40, and 60 trading days). Models (1)-(6) and (7)-(12) examine the impact of short-selling permission and ban, respectively. Definitions of the variables are described in Panel A of Table 2. Parentheses report t-statistics based on standard errors adjusted for heteroscedasticity. *, **, and *** indicate significance at the 10%, 5%, and 1% levels, respectively.

Regression models to examine effects of short-selling permission Regression models to examine effects of short-selling ban

20d(Short-selling volume divided by trading volume) 40d(Short-selling volume divided by trading volume) 60d(Short-selling volume divided by trading volume) 20d(Short-selling volume divided by trading volume) 40d(Short-selling volume divided by trading volume) 60d(Short-selling volume divided by trading volume)

Larger control group Smaller control group Larger control group Smaller control group Larger control group Smaller control group Larger control group Smaller control group Larger control group Smaller control group Larger control group Smaller control group
Model (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12)
Index_in 0.0005 -0.0018 -0.0018 -0.0019 -0.0047* -0.0041*
(0.17) (-0.70) (-0.77) (-0.99) (-2.20) (-1.96)
Y2021 -0.0064 -0.0051 -0.0036 -0.0072 0.0048 0.002 -0.0018 -0.0055 -0.0027 -0.0074 0.0060* 0.0028
(-1.58) (-1.07) (-0.58) (-1.00) (1.30) (0.97) (-1.34) (-1.36) (-0.49) (-1.13) (1.83) (1.46)
Index_in×Y2021 0.0642*** 0.0629*** 0.0887** 0.0743*** 0.0744** 0.0660**
(11.61) (11.15) (2.90) (4.22) (2.43) (2.97)
Index_out -0.0022 -0.0004 0.0042 -0.0022 -0.0011 -0.0042*
(-0.87) (-0.26) (0.57) (-1.64) (-0.26) (-1.91)
Index_out×Y2021 -0.0583*** -0.0554*** -0.0486*** -0.0412*** -0.0476*** -0.0419***
(-6.88) (-6.12) (-6.22) (-4.65) (-6.61) (-6.78)

ln(Market cap.) -0.0039 -0.0023 -0.0016 -0.001 0.0023 0.0016 0.0023* 0.0006 0.0022 0.0018 0.0063*** 0.0053*
(-1.77) (-1.39) (-0.63) (-0.48) (1.01) (0.46) (1.97) (0.42) (1.48) (0.99) (3.53) (2.13)
ln(Trading vol.) 0.0003 -0.0002 0.0049 0.001 0.0038 0.0025 0.0002 -0.0002 0.0021 0.0006 0.0003 -0.0004
(0.28) (-0.23) (1.21) (1.06) (1.55) (1.47) (0.30) (-0.22) (0.84) (0.41) (0.31) (-0.59)
KOSPI 0.0047* 0.0042 -0.0002 0.0018 -0.003 -0.003 -0.0061** -0.0098*** -0.0098*** -0.0124*** -0.0106*** -0.0144***
(1.91) (0.94) (-0.05) (0.34) (-1.13) (-0.53) (-2.52) (-4.91) (-3.48) (-3.82) (-5.74) (-5.78)
Industry fixed effects Included Included Included Included Included Included Included Included Included Included Included Included

R-squared 0.1753 0.1157 0.0922 0.2171 0.1105 0.2814 0.4405 0.1453 0.1442 0.0777 0.0761 0.0743
# of obs. 528 301 533 302 538 307 330 306 537 306 536 305
Model-p 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

<Table 4>

Effects of short-selling permission/ban on price efficiency

Note. This table reports the main results where the dependent variable is changes in price efficiency measures. We calculate Hou and Moskowitz’s (2005) measures, Price delay 1 or 2, for each stock and take its difference between 60 trading days before and after the index update. Models (1)-(4)and (5)-(8) examine the impact of short-selling permission and ban, respectively. Definitions of the variables are described in Panel A of Table 2. Parentheses report t-statistics based on standard errors adjusted for heteroscedasticity. *, **, and *** indicate significance at the 10%, 5%, and 1% levels, respectively.

Regression models to examine effects of short-selling permission Regression models to examine effects of short-selling ban

60d(Price delay 1) 60d(Price delay 2) 60d(Price delay 1) 60d(Price delay 2)

Larger control group Smaller control group Larger control group Smaller control group Larger control group Smaller control group Larger control group Smaller control group

Model (1) (2) (3) (4) (5) (6) (7) (8)
Index_in 0.0139 0.0229 0.0068 -0.0028
(0.32) (0.50) (0.19) (-0.08)
Y2021 -0.2101*** -0.1943*** -0.2852*** -0.2862*** -0.2560*** -0.2695*** -0.3162*** -0.3126***
(-11.80) (-8.48) (-20.60) (-12.53) (-12.21) (-9.92) (-15.63) (-11.51)
Index_in×Y2021 -0.1432** -0.1545** -0.0971** -0.0969*
(-1.97) (-2.06) (-2.93) (-2.06)
Index_out -0.0107 -0.0293 0.0137 0.0137
(-0.22) (-0.60) (0.28) (0.27)
Index_out×Y2021 0.0311 0.0482 -0.0500 -0.0527
(0.39) (0.59) (-0.69) (-0.71)

ln(Market cap.) -0.0028 -0.0086 0.0100 0.0051 -0.0035 -0.0057 -0.0106 -0.0187
(-0.30) (-0.71) (1.93) (0.64) (-0.34) (-0.45) (-1.10) (-1.52)
ln(Trading vol.) -0.0078 -0.0075 -0.0111** -0.0185** 0.0024 -0.0001 -0.0032 -0.0126
(-1.13) (-0.82) (-2.52) (-3.09) (0.29) (-0.01) (-0.41) (-1.17)
KOSPI 0.0102 -0.0032 -0.0137 -0.0054 0.0419* 0.0511* -0.0009 -0.0034
(0.55) (-0.13) (-0.98) (-0.46) (1.80) (1.70) (-0.04) (-0.12)
Industry fixed effects Included Included Included Included Included Included Included Included

R-squared 0.1704 0.1739 0.1924 0.1841 0.1937 0.2193 0.2842 0.2809
# of obs. 556 322 561 325 348 217 348 213
Model-p 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000

<Table 5>

Effects of short-selling permission/ban on stock returns

Note. This table reports the main results where the dependent variable is stock returns for the next 20, 40, and 60 trading days after the index updates. Models (1)-(6) and (7)-(12) examine the impact of short-selling permission and ban, respectively. Definitions of the variables are described in Panel A of Table 2. Parentheses report t-statistics based on standard errors adjusted for heteroscedasticity. *, **, and *** indicate significance at the 10%, 5%, and 1% levels, respectively.

Regression models to examine effects of short-selling permission Regression models to examine effects of short-selling ban

Stock returns for the next 20 days Stock returns for the next 40 days Stock returns for the next 60 days Stock returns for the next 20 days Stock returns for the next 40 days Stock returns for the next 60 days

Larger control group Smaller control group Larger control group Smaller control group Larger control group Smaller control group Larger control group Smaller control group Larger control group Smaller control group Larger control group Smaller control group
Model (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12)
Index_in -0.0534*** -0.0536** -0.1415** -0.1442** -0.2044** -0.2126**
(-3.80) (-2.80) (-2.84) (-2.40) (-3.00) (-2.58)
Y2021 -0.0443** -0.029 -0.1359*** -0.1424*** -0.2059*** -0.2297*** -0.0166 0.0164 -0.0976*** -0.0600*** -0.1309** -0.1053**
(-2.83) (-1.36) (-4.67) (-4.48) (-6.92) (-5.41) (-1.83) (0.94) (-4.24) (-3.52) (-3.47) (-3.08)
Index_in×Y2021 0.0554*** 0.0391 0.1076* 0.1162** 0.1735** 0.2028**
(3.25) (1.66) (1.98) (2.31) (2.42) (2.86)
Index_out -0.0008 0.0112 0.0256 0.0867** 0.0273 0.1105
(-0.05) (0.64) (0.59) (3.34) (0.30) (1.51)
Index_out×Y2021 -0.0382* -0.0682* -0.0723* -0.0960* -0.0467 -0.0641
(-2.08) (-2.06) (-2.13) (-2.30) (-0.66) (-1.04)

ln(Market cap.) -0.0035 0.0031 -0.002 0.0024 -0.0154* -0.0173 -0.004 -0.0065 -0.0173 -0.0348* -0.0297 -0.0481**
(-0.41) (0.32) (-0.22) (0.18) (-1.92) (-1.40) (-1.24) (-1.15) (-1.10) (-2.28) (-1.44) (-2.47)
ln(Trading vol.) 0.0213*** 0.0132 0.0303** 0.0226* 0.0600*** 0.0573*** 0.0142** 0.0263*** 0.0304*** 0.0353** 0.0396*** 0.0344**
(3.72) (1.67) (2.80) (1.88) (4.14) (4.92) (2.90) (4.13) (6.11) (3.20) (5.40) (2.46)
KOSPI 0.0013 0.0117 -0.0160* -0.0047 -0.0018 0.0483 0.0215* 0.0337** 0.0518 0.0529 0.0643 0.0838
(0.14) (0.45) (-1.85) (-0.18) (-0.16) (1.63) (2.06) (2.49) (1.41) (1.01) (1.16) (1.83)
Industry fixed effects Included Included Included Included Included Included Included Included Included Included Included Included

R-squared 0.0505 0.0417 0.104 0.1144 0.1394 0.1573 0.0655 0.124 0.1667 0.1833 0.1794 0.1797
# of obs. 558 323 563 327 558 321 354 221 356 221 354 220
Model-p 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0000 0.0001 0.0000 0.0000 0.0000 0.0000

<Table 6>

Effects of short-selling permission/ban on stock volatility

Note. This table reports the main results where the dependent variable is changes in stock volatility. We calculate a variance of daily stock returns for each stock and take its ratio of the difference between before and after the index updates (based on 20, 40, and 60 trading days) to the before value. Models (1)-(6) and (7)-(12) examine the impact of short-selling permission and ban, respectively. Definitions of the variables are described in Panel A of Table 2. Parentheses report t-statistics based on standard errorsadjusted for heteroscedasticity. *, **, and *** indicate significance at the 10%, 5%, and 1% levels, respectively.

Regression models to examine effects of short-selling permission Regression models to examine effects of short-selling ban

20d(Stock volatility) 40d(Stock volatility) 60d(Stock volatility) 20d(Stock volatility) 40d(Stock volatility) 60d(Stock volatility)

Larger control group Smaller control group Larger control group Smaller control group Larger control group Smaller control group Larger control group Smaller control group Larger control group Smaller control group Larger control group Smaller control group
Model (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) (12)
Index_in -0.3435*** -0.4736*** -0.2671** -0.3214** -0.3103*** -0.4002***
(-8.67) (-5.32) (-2.70) (-2.57) (-8.06) (-3.87)
Y2021 -0.5797*** -0.8387*** -0.2127** -0.3096 -0.0436 -0.182 -0.5345*** -0.5078*** -0.1882** -0.2859** 0.0165 -0.0225
(-5.52) (-7.53) (-2.70) (-1.19) (-1.42) (-1.16) (-3.77) (-3.86) (-2.71) (-2.49) (0.26) (-0.21)
Index_in×Y2021 0.2279 0.4846** 0.1838 0.2772 0.1455 0.2838
(1.57) (2.99) (0.89) (0.73) (1.38) (1.31)
Index_out -0.2250*** -0.2829*** -0.0692 -0.1042** -0.1715 -0.0639
(-3.52) (-7.70) (-1.18) (-2.60) (-1.85) (-0.78)
Index_out×Y2021 0.2541 0.1859 -0.0054 0.0842 0.0725 0.0963
(1.66) (1.04) (-0.05) (0.47) (0.69) (0.59)

ln(Market cap.) -0.0335 -0.0206 -0.0417 0.0115 -0.0031 0.0423 -0.1034* -0.0424 -0.0464 -0.0168 0.0003 0.0091
(-0.69) (-0.43) (-1.46) (0.25) (-0.14) (1.33) (-2.14) (-0.92) (-1.12) (-0.43) (0.01) (0.33)
ln(Trading vol.) 0.0135 -0.0055 0.0462** 0.0159 0.0342 0.0115 0.0405 0.0477 0.0326 0.0275 0.0304 -0.0009
(0.42) (-0.20) (2.89) (1.28) (1.74) (0.33) (1.03) (0.85) (1.54) (0.80) (1.68) (-0.04)
KOSPI -0.0338 -0.0143 -0.0397 -0.0871* -0.0867* -0.1294*** -0.0288 -0.0324 -0.0742 -0.1246 -0.0981 -0.0853
(-0.51) (-0.26) (-1.21) (-2.10) (-1.98) (-6.67) (-0.46) (-0.23) (-1.34) (-0.84) (-1.72) (-0.87)
Industry fixed effects Included Included Included Included Included Included Included Included Included Included Included Included

R-squared 0.1359 0.165 0.0662 0.0697 0.0427 0.0502 0.1661 0.1857 0.1051 0.2063 0.0718 0.133
# of obs. 558 325 566 328 564 328 350 218 350 218 353 221
Model-p 0.0000 0.0000 0.0000 0.0000 0.0009 0.0000 0.0000 0.0000 0.0000 0.0000 0.0304 0.0000

Appendix A

Stocks in the treatment group (in Korean)

Treatment group Index-in = 1 Index-out = 1
June 12, 2020 HMM 에스엘
포스코케미칼 신라젠
F&F 넥슨게임즈
한진칼 효성중공업
KG스틸 한국쉘석유
아시아나항공 동양
케어젠 남양유업
차바이오텍 한양이엔지
화승엔터프라이즈 JW홀딩스
유진테크 현대리바트
아이티엠반도체 하이록코리아
더블유게임즈 대덕
쿠쿠홈시스 세종텔레콤
상상인 AK홀딩스
KH바텍 태웅
우리기술투자 아스트
다우데이타 이엠코리아
셀리버리 에스엠코어
이베스트투자증권 우리산업
유비쿼스홀딩스 SGC이테크건설
태영건설 강스템바이오텍
코윈테크 코스맥스엔비티
현대바이오랜드
브이티지엠피
December 11, 2020 하이브 동아쏘시오홀딩스
카카오게임즈 세아베스틸지주
한화시스템 남해화학
키움증권 동아에스티
씨에스윈드 바텍
두산퓨얼셀 우리기술투자
솔브레인 CJ프레시웨이
대웅 디오
피엔티 한라홀딩스
대주전자재료 롯데푸드
신풍제약 성우하이텍
지누스 모두투어
엘앤씨바이오 인바디
삼양식품 지노믹트리
코리아센터 휴온스글로벌
상아프론테크 성광벤드
메드팩토 대교
에스앤에스텍 나스미디어
한국기업평가 코윈테크
동국S&C 연우
제이앤티씨 파워로직스
노바렉스 미래컴퍼니
서울바이오시스 한국전자금융
남선알미늄
알서포트
레몬
June 11, 2021 SK바이오사이언스 케어젠
SK아이이테크놀로지 골프존
대한전선 SPC삼립
효성첨단소재 삼양사
효성티앤씨 빙그레
심텍 한일현대시멘트
하나머티리얼즈 사람인에이치알
티에스이 신흥에스이씨
동원산업 애경산업
삼강엠앤티 HDC
파크시스템스 한국기업평가
박셀바이오 이지홀딩스
데브시스터즈 클리오
젬백스 노바렉스
두산테스나 태영건설
우리기술투자 남선알미늄
바이넥스 비츠로셀
에프에스티 에스티큐브
성우하이텍 드림어스컴퍼니
유니슨 에이치엘사이언스
아주IB투자 현대바이오랜드
아이큐어 브이티지엠피
네오팜
December 10, 2021 현대중공업 이노션
카카오페이 F&F홀딩스
메리츠금융지주 삼양식품
에스엘 LX홀딩스
HK이노엔 엔케이맥스
PI첨단소재 롯데하이마트
명신산업 일양약품
원익QnC LX하우시스
SBW생명과학 메디포스트
바이오니아 HLB테라퓨틱스
에코프로에이치엔 동국S&C
코미코 크리스탈지노믹스
한국비엔씨 유비쿼스홀딩스
티케이케미칼 와이솔
압타바이오 위닉스
그래디언트 슈피겐코리아
코나아이 아이큐어
휴온스글로벌 유틸렉스
엠투엔 텔콘RF제약
셀리드 레몬
케이피엠테크

Appendix B

Stocks those are newly-listed within 6 months at the index update date (in Korean)

Stock Index’s regular update

Year Month
현대중공업 2021 12
카카오페이 2021 12
SK바이오사이언스 2021 6
SK아이이테크놀로지 2021 6
하이브 2020 12
F&F 2021 6
카카오게임즈 2020 12
솔브레인 2020 12
DL이앤씨 2020 12
DL이앤씨 2021 6
대덕전자 2020 6
티와이홀딩스 2020 12
HK이노엔 2021 12
PI첨단소재 2021 12
KCC글라스 2020 6
LX홀딩스 2021 6
에코프로에이치엔 2021 6
엠씨넥스 2021 6
엠씨넥스 2021 12
제이앤티씨 2020 6
서울바이오시스 2020 6
켄코아에어로스페이스 2020 6