Several recent papers have tested the permanent income-cum-rational expectations hypothesis using data on nondurable or semidurable consumption. We show how this approach can be extended to the case of durables. An application to panel data on automobile expenditures reveals no evidence against the permanent income hypothesis. This result is unchanged in subsamples segregated by family holdings of liquid assets.

The optimal timing of real investment is studied under the assumptions that investment is irreversible and that new information about returns is arriving over time. Investment should be undertaken in this case only when the costs of deferring the project exceed the expected value of inforrnation gained by waiting. Uncertainty, because it increases the value of waiting for new information, retards the current rate of investment. The nature of investor's optimal reactions to events whose implications are resolved over time is a possible explanation of the instability of aggregate investment over the business cycle.

Financial stability is an important goal of policy, but the relation of financial stability to economic performance and even the meaning of the term itself are poorly understood. This paper explores these issues in a theoretical model. We argue that financial instability, or fragility, occurs when entrepreneurs who want to undertake investment projects have low net worth; the heavy reliance on external finance that this implies causes the agency costs of investment to be high. High agency costs in turn lead to low and inefficient investment. Standard policies for fighting financial fragility can be interpreted as transfers that maintain or increase the net worth of potential borrowers.

Structural vector autoregressions (VARs) are widely used to trace out the effect of monetary policy innovations on the economy.However, the sparse information sets typically used in these empirical models lead to at least two potential problems with the results.First, to the extent that central banks and the private sector have information not reflected in the VAR, the measurement of policy innovations is likely to be contaminated.A second problem is that impulse responses can be observed only for the included variables, which generally constitute only a small subset of the variables that the researcher and policymaker care about.In this paper we investigate one potential solution to this limited information problem, which combines the standard structural VAR analysis with recent developments in factor analysis for large data sets.We find that the information that our factor-augmented VAR (FAVAR) methodology exploits is indeed important to properly identify the monetary transmission mechanism.Overall, our results provide a comprehensive and coherent picture of the effect of monetary policy on the economy.