Stock Price Patterns around the Trades of Corporate Insiders on the London Stock Exchange

Stock Price Patterns around the Trades of Corporate Insiders on the London Stock Exchange1 Sylvain Friederich,2;3 Alan Gregory, John Matatko, and Ian Tonks. September 1999 1We thank Margaret Bray, Bob Nobay, Richard Payne, seminar participants at the LSE for comments. Remaining errors are, of course, ours. 2Corresponding author. Tel: (+44-207) 955-7893. Email: s.j.friederich@lse.ac.uk 3The authors are respectively a¢liated with the Financial Markets Group, London School of Economics and TEAM, Université de Paris - I (Friederich), the School of Business and Management, University of Exeter (Gregory and Matatko), and the Financial Markets Group, LSE and Department of Economics, University of Bristol (Tonks). Abstract Résumé français: Les exigences de transparence des marchés …nanciers anglo-saxons sont traditionellement élevées, et les autorités de régulation exigent notamment de toute personne exerçant des fonctions de responsabilité dans un entreprise qu’elle révèle au marché tous les achats ou ventes de titres de leurs sociétés qu’elle e¤ectue. Dans cette étude, nous examinons le contenu informationnel de l’annonce de telles transactions sur le marché de Londres, en mesurant les rendements anormaux qui précèdent et suivent ces transactions. Les résultats indiquent la présence de rendements anormaux survenant avant et après la communication au marché de ces achats ou ventes. Il semble que la règlementa-tion …nancière britannique, qui interdit la réalisation de pro…ts basés sur des mouve-ments de prix de court terme et une information d’initié, ait été ignorée par un certain nombre d’agents au cours de la période d’échantillon (1986-1994). En conformité avec l’hypothèse d’e¢cience semi-forte cependant, il apparaît également que ces rendements anormaux de court terme ne sont plus statistiquement di¤érents de zéro après que des coûts de transactions moyens ont été pris en compte. Un autre résultat est que certaines catégories de transactions permettent de prévoir des rendements anormaux futurs plus élevés. En particulier, selon l’hypothèse de “stealth trading” (“transactions furtives”) mise en avant par Brown et Warner (1993), les transactions de taille moyenne devraient être celles au contenu informationnel le plus grand, indiquant que des agents prennent des positions de portefeuille importantes tout en tentant de ne pas attirer l’attention d’autres opérateurs de marché ou des autorités de régulation. Nos résultats sont con-formes à cette hypothèse et indiquent que les transactions de taille moyenne sont en moyenne suivies de rendements anormaux positifs comparativement importants. Mots-clés : Transactions d’initiés, transactions d’agents informés, tests d’e¢cience des marchés. Classi…cation JEL : G 14 English abstract: This paper examines the patterns of security returns around the trades of corporate insiders in the shares of their own company. We …nd patterns in abnormal returns in the days around a director’s trade that are consistent with directors engaging in short-term market timing: they sell (buy) after an increase (decline) in prices, and their trades are followed by a partial price reversal. This provides strong evidence that directors trade to exploit patterns in share prices. We also …nd positive gross, but not net, abnormal returns to imitating some of the trades of directors once transactions costs implicit in the bid-ask spread are taken into account. We also report that some types of trades have superior predictive content over future returns. In particular, we …nd that medium-sized trades are more informative for short-term returns than large ones, consistent with Barclay and Warner’s (1993) “stealth trading” hypothesis. Keywords: market e¢ciency, corporate insiders, insider trading, Directors’ trading, informed trading. JEL Classi…cation: G 14 2 1 Introduction Do the actions of corporate insiders convey information about future company prospects which are not availableelsewhere? From thepoint of viewoftestingfor market e¢ciency, one issue is whether corporate insiders have the ability to time the market, and con-sequently generate bene…ts, either for their …rms, or for themselves personally. If they are able to generate abnormal pro…ts, this could be interpreted as evidence against strong-form e¢ciency. Typically, …nancial regulators assume that corporate insiders’ in-formation is superior, and require that their actions be disclosed to the market. This leads to a second issue, of whether outsiders may obtain excess returns from mimicking the signals sent by the insiders’ actions.1 Signi…cant abnormal returns following an in-sider’s trade could be interpreted as evidence against semi-strong e¢ciency. Examples of actions potentially timed to bene…t the …rm are stock splits or issues, corporate repur-chases or restructurings. An example of an action timed to bene…t the corporate insider personally, and which typically must be disclosed after it has occurred is the trade of a corporate insider in the shares of his company.2 This is the event that this paper focuses on. In previous work, although there was evidence of long-run abnormal returns following the trades of corporate insiders, returns during the month (or even the two weeks) containing the trade were found to be not signi…cantly di¤erent from zero. The current paperthereforeexamines thebehaviourofdaily returns immediatelyaroundthetrades of corporate insiders. First, we identify patterns of price movements around the directors’ trades which may provide evidence of trading on short-lived information as de…ned for instance in Admati and P‡eiderer (1988). This takes us closer to strong-form e¢ciency tests and to the debates on the detection and regulation of insider trading. Secondly, we ascertain the size of excess returns over the …rst month around the director’s trade, in 1Appendix 1 gives more evidence on the interest that currently surrounds data on these trades among professional investors. 2Since both types of events are voluntary, they can be linked as in Bagnoli and Khanna (1992), in which the corporate event and the manager’s expected pro…t from trading in his company’s stocks are jointly determined. An empirical literature tying corporate transactions in the primary market and the manager’s personal payo¤ in the secondary market has also developed. Examples are Karpo¤ and Lee (1991) and Lee (1997). 1 order to examine the pro…tability of a mimicking strategy in the short-term, and taking explicitly “round-trip” (spread) transaction costs into account. We report evidence of trading around short-term price changes by corporate insiders over the sample period (October 1986-November 1994), in spite of regulatory arrange-ments. This provides strong evidence that directors trade to exploit patterns in share prices. Although these patterns are statistically signi…cant, their economic signi…cance is not necessarily a cause of great concern. Once an adjustment is made for transaction costs, potential short-term abnormal returns to outsiders are more or less whittled down to zero. We also report that some signals dominate others in terms of predictive contents over future returns. Buy trades are followed on average by larger abnormal returns than sell trades. Yet an important di¤erence with earlier work is that clustered trades strongly dominate large ones in terms of signal strength. We …nd that most of these trades are of medium size, and generally report evidence that medium-sized trades as a whole seem more informative than large ones. This is consistent with the “stealth trading” hypothesis of Barclay and Warner (1993). The most plausible interpretation is that informed traders try to make their trading on short-lived information less conspicuous to both market participants and regulatory bodies by avoiding block trades. 1.1 Related prior research A long literature has developed examining whether corporate insiders seem to bene-…t from their trades and whether strategies mimicking these trades may also produce abnormal returns in the medium to long run. Early work in the US by Ja¤e (1974) and Finnerty (1976) identi…ed excess returns in the …rst few months after the director’s trade, which suggests that insiders are able to predict and exploit future returns. How-ever, this apparent semi-strong form ine¢ciency was explained away in a later study by Seyhun (1986) in terms of (estimated) transactions costs of trading. Further work by Bettis, Vickrey, and Vickrey (1997) reports that abnormal pro…ts can be made when focusing only on the insiders’ block trades (over 10,000 shares, following the de…nition of blocks used in US markets) as a signal, using again a measure of estimated transactions costs of mean spreads plus mean commissions. Lakonishok and Lee (1998) examine the 2 ... - tailieumienphi.vn