Short sellers are routinely blamed for destabilizing stock markets by exacerbating deviations from fundamental values. In response, regulators periodically impose short sale constraints aimed at preventing excessive stock market declines. One explanation is that policy makers regard short sellers as behaving like positive feedback traders. Relying on the theoretical model put forward by Sentana and Wadhwani (1992), which stresses the conditional nature of returns’ persistence, bans on selected financial stocks in six countries during the 2008/2009 global financial crisis are examined. These provide us with a setting to analyze the impact of short sale restrictions on feedback trading. Our findings suggest that, in the majority of markets examined, restrictions of this kind amplify positive feedback trading during periods of high volatility and, hence, contribute to stock market downturns. On balance then, short selling bans do not contribute to enhancing financial stability.

In this paper, we provide empirical evidence on the impact of institutional investors on stock market returns dynamics. The Polish pension system reform in 1999 and the associated increase in institutional ownership due to the investment activities of pension funds are used as a unique institutional characteristic. Performing a Markov-switching-GARCH analysis we find empirical evidence that the increase of institutional ownership has temporarily changed the volatility structure of aggregate stock returns. The results are interpretable in favor of a stabilizing effect on index stock returns induced by institutional investors.

In this paper, we challenge the often implemented herding measure by Chang et al. (2000). They regress the cross-sectional absolute deviation of returns on the absolute and squared excess market return. A coefficient on the squared excess market return significantly smaller than zero is interpreted as evidence for herding. However, we show that the true coefficient is positive under the null hypothesis of no herding. Hence, their test is biased against finding evidence in favour of herding. Empirical examinations for the S&P 500 and the EuroStoxx 50 confirm the misleading implications of Chang, Cheng and Khorana’s measure, while our modified test provides clear-cut evidence for herding behaviour.

In this paper, we ask whether the Bundesbank, prior to the European Central Bank taking responsibility for monetary policy in 1999, reacted systematically to stock price movements. In contrast to the results for the US, our empirical findings show a generally weak relationship between German stock returns and short-term interest rates at the daily and the monthly frequency. The results are extremely robust to alternative model specifications. The evidence is inconsistent with the hypothesis of a systematic reaction of the Bundesbank to German stock prices. However, we do find that, as in the US, the Bundesbank may have reacted to the stock market crash of 1987 by loosening monetary policy.