This paper examines the impact on the liquidity of NYSE/AMEX listed stocks when they were subsequently listed on the London or the Tokyo Stock Exchanges. It can be argued that the increased competition from foreign market makers will reduce the monopoly rents that specialists can earn, thereby improving their quotes. We find, however, that spreads do not decrease following a dual listing, though the depth of the quotes increases as predicted. The apparent increase in depth disappears once we account for changes in price, volume and return variance. We also find that the level of informed trading increases, which increases the cost to the specialist of providing liquidity, and explains why spreads do not decline in spite of increased competition. Consistent with an increase in informed trading, we also document an increase in trading activity.

We study the price effects of changes to the S&P 500 index and document an asymmetric price response: There is a permanent increase in the price of added firms but no permanent decline for deleted firms. These results are at odds with extant explanations of the effects of index changes that imply a symmetric price response to additions and deletions. A possible explanation for asymmetric price effects arises from the changes in investor awareness. Results from our empirical tests support the thesis that changes in investor awareness contribute to the asymmetric price effects of S&P 500 index additions and deletions.