This paper examines the power of statistical tests commonly used to examine the efficiency of speculative markets. It shows that for markets with "long horizons" such as the stock markets, or the market for long term bonds, these tests have very low power. Market valuations can differ...

This paper summarizes our earlier research documenting the characteristic speculative dynamics of many asset markets and suggests a framework for understanding them. Our model incorporates "feedback traders," traders whose demand is based on the history of past returns rather than the...

This paper presents evidence on the characteristic speculative dynamics of a wide range of asset returns. It highlights three stylized facts. First, returns tend to be positively serially correlated at high frequency. Second, returns tend to be negatively serially correlated over long horizons....

Analyses of the role of rational speculators in financial markets usually presume that such investors dampen price fluctuations by trading against liquidity or noise traders. This conclusion does not necessarily hold when noise traders follow positive-feedback investment strategies buy when...

We use the revised estimates of U.S. GNP constructed by Christina Romer (1989) to assess the time-series properties of U.S. output per capita over the past century. We reject at conventional significance levels the null that output is a random walk in favor of the alternative that output is a...

The claim that financial markets are efficient is backed by an implicit argument that misinformed "noise traders" can have little influence on asset prices in equilibrium. If noise traders' beliefs are sufficiently different from those of rational agents to significantly affect prices, then...