In 2008, U.S. regulators banned the short-selling of financial stocks, fearing that the practice was helping to drive the steep drop in stock prices during the crisis. However, a new look at the effects of such restrictions challenges the notion that short sales exacerbate market downturns in this way. The 2008 ban on short sales failed to slow the decline in the price of financial stocks; in fact, prices fell markedly over the two weeks in which the ban was in effect and stabilized once it was lifted. Similarly, following the downgrade of the U.S. sovereign credit rating in 2011—another notable period of market stress—stocks subject to short-selling restrictions performed worse than stocks free of such restraints.
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Recent research on the 2008 bans allows us to assess the costs and benefits of short-selling restrictions. The preponderance of evidence suggests that the bans did little to slow the decline in the prices of financial stocks. In addition, the bans produced adverse side effects: Trading costs in equity and options markets increased, and stock and options prices uncoupled.
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Taken as a whole, our research challenges the notion that banning short sales during market downturns limits share price declines. If anything, the bans seem to have the unwanted effects of raising trading costs, lowering market liquidity, and preventing short-sellers from rooting out cases of fraud and earnings manipulation. Thus, while short-sellers may bear bad news about companies’ prospects, they do not appear to be driving price declines in markets.