The first essay investigates the effects of the introduction of index-tracking stocks for the Dow Jones Industrial Average and NASDAQ 100 on the liquidity of the underlying securities. There is evidence of increased liquidity. Specifically, quoted and effective spreads decrease. Also, the adverse selection component of effective spread decreases while the direct cost component remains unchanged. These findings are consistent with increased liquidity due to index arbitrage. Consistent with the diversification of firm-specific information in a composite security, the index-tracking stock has lower relative spread and adverse selection costs as compared to a price weighted composite of the underlying stocks. The second essay investigates the l...