The effect that the entry of additional firms has on consumer welfare and efficiency in a simple equilibrium-search model is considered. Special attention is given to the case where an arbitrageur enters. It is shown that entry can increase the monopoly power of firms and so reduce welfare. In particular, arbitrage always makes consumers worse off and can increase price dispersion and reduce efficiency in the market. The source of the results is that, unlike other forms of product differentiation, the amount of monopoly power that firms have in a search model is determined endogenously by consumers.

Friedman's (1960) proposal to pay interest on (required) reserves is considered in a setting that eliminates the indeterminacy of steady-state equilibrium discussed by Sargent and Wallace (1985). In an overlapping-generations model where the real rate of interest is technologically determined, the payment of interest on reserves results in a determinate, Pareto optimal steady-state equilibrium. However, interest payments on reserves reduce the steady-state welfare of all young agents and, for many economies, result in the existence of stationary sunspot equilibria. This is the case even if such equilibria cannot exist when reserves do not earn interest.

An endogenous growth model with multiple assets is developed. Agents who face random future liquidity needs accumulate capital and a liquid, but unproductive asset. The effects of introducing financial intermediation into this environment are considered. Conditions are provided under which the introduction of intermediaries shifts the composition of savings toward capital, causing intermediation to be growth promoting. In addition, intermediaries generally reduce socially unnecessary capital liquidation, again tending to promote growth.

This paper presents and implements statistical tests of stock-market forecastability and volatility that are immune from the severe statistical problems of earlier tests. It finds that although the null hypothesis of market efficiency is rejected, the rejections are only marginal. The paper also shows how volatility tests and recent regression tests are closely related, and demonstrates that when finite sample biases are taken into account, regression tests also fail to provide strong evidence of violations of the conventional valuation model.