Short Sales Constraints and Financial Stability: Evidence from the Spanish 2011 Ban

This paper studies the main effects of the short sales ban implemented in August 2011 in the Spanish stock market along two dimensions: financial stability and market performance. Regarding the first, we show that short positions were a significant determinant of the probability of default of medium-sized banks before the ban. We find that, by weakening the contagion effect coming from the sovereign risk, the ban helped stabilise the probability of default of medium-sized banks, an effect which is not significant in the case of the largest banks and non-financials. Nonetheless, the stabilising power of the ban came at the cost of a large decline in the relative liquidity, trading volumes and price information efficiency of medium-sized banks’ stocks.