Implications of factor-based asset pricing models for estimation of expected returns and for portfolio selection are investigated. In the presence of model mispricing due to a missing risk factor, the mispricing and the residual covariance matrix are linked together. Imposing a strong form of...

We investigate the portfolio choices of mean-variance-optimizing investors who use sample evidence to update prior beliefs centered on either risk-based or characteristic-based pricing models. With dogmatic beliefs in such models and an unconstrained ratio of position size to capital, optimal...

The collapse of a fixed exchange rate is typically marked by a sudden balance-of-payments crisis in which"speculators" fleeing from the domestic currency acquire a large portion of the central bank's foreign exchange holdings.Faced with such an attack, the central bank often withdraws...

The paper develops a model of exchange-rate and current-account determination for a small economy peopled by infinitely lived, utility-maximizing households. In this setting, a central-bank purchase of foreign exchange has no real effects when central-bank foreign reserves earn interest at the...

This paper investigates the long- and short-run neutrality of open-market monetary policy in a world of fixed exchange rates and imperfect substitutability between bonds denominated in different currencies. Using an illustrative portfolio-balance model, it shows that when the public discounts...

We argue that active management's popularity is not puzzling despite the industry's poor track record. Our explanation features decreasing returns to scale: As the industry's size increases, every manager's ability to outperform passive benchmarks declines. The poor track record occurred before...

We survey the recent literature on learning in financial markets. Our main theme is that many financial market phenomena that appear puzzling at first sight are easier to understand once we recognize that parameters in financial models are uncertain and subject to learning. We discuss phenomena...

Even when the exchange-rate plays no expenditure-switching role, countries may wish to have flexible exchange rates in order to free the domestic interest rate as a stabilization tool. In a setting with nontraded goods, exchange-rate movements may also enhance international risk sharing