Three Essays On Market Efficiency And Corporate Diversification

In my first essay, I use additions to the S&P 500 index as a laboratory to investigate how the interaction between arbitrageurs and arbitrage risk affects security prices. I find that the price effect is strong when there is high arbitrage risk (as measured by the lack of close substitutes) and low presence of arbitrageurs (as measured by low ownership by active institutions). Furthermore, a strong presence of arbitrageurs moderates the effect of arbitrage risk on the post-addition price reaction of added stocks. I also find a significant decrease in arbitrageurs' ownership in the added stocks post addition. More importantly, this decrease is accompanied by a significant increase in arbitrageurs' ownership in the added stocks' close substitutes.