Before revision:  Stock distance effect is further studied, where companies are found to more likely set their headquarters close to each other. In the normal market environment, the stock correlation decays with the stock distance , but is independent of the stock distance in and after the financial crisis .
After revision:  Stock distance effect is further studied, with a crossover behavior observed for the stock distance distribution. The probability of the short distance is much greater than that of the long distance. The average stock correlation is found to weakly decay with the stock distance , but is independent of the stock distance in and after the financial crisis .