Finance theory suggests that the sub-optimal international portfolio investment bias of home and foreign investors should affect the cost of capital of a country through its influence on the degree of international market integration/segmentation. Using four unique proxies of aggregate market level cost of capital measures and three different measures of sub-optimal international equity portfolio allocations by home and foreign investors, we find compelling evidence supporting the theory that countries which demonstrate higher home bias are associated with higher cost of capital. Similarly, consistent with theory we also find that countries which are favoured by foreign investors, relative to theoretical prescription, are associated with lo...