The authors examine the impact of changes in equity-option margin requirements on the liquidity of options and underlying stock markets. They find that the decrease in margin was associated with an increase in spreads and trade informativeness, and a decrease in depth for the underlying stocks....

This paper investigates the behavior of stock and option prices around block trades in stocks. The results indicate that for both uptick and downtick block trades the stock prices adjust within a fifteen minute period after the block trade. Moreover, for uptick blocks there is no evidence of any...