Collective fineness of stock prices and efficiency of financial markets

Recent literature exploring the efficiency properties of options has examined the conditions under which incomplete financial markets would be equivalent to the Arrow-Debreu model. A usual assumption made in establishing such an equivalence is that some security price is ‘fine’ on the state space. This assumption is relaxed. Under more realistic assumptions it is shown that any portfolio is fine and options written on it can bring about complete markets.     

Trade openness and the informational efficiency of emerging stock markets

This paper examines the empirical link between trade openness and the informational efficiency of stock markets in 23 developing countries. Our fixed effects panel regression results document a significant negative relation between trade openness and stock return autocorrelations only when the de facto measure is used. On this basis, we argue that a greater level of de facto trade openness is associated with a higher degree of informational efficiency in these emerging stock markets because the former signals higher future firm profitability, and investors tend to react faster to information when there is less uncertainty about a firm's future earnings or cash flows. Further analyses find no significant association between the extent of financial openness and the degree of informational efficiency.