Previous empirical studies have uncovered little evidence that police reduce crime, possibly due to simultaneity problems. This paper uses the timing of mayoral and gubernatorial elections as an instrumental variable to identify a causal effect of police on crime. Increases in the size of police forces are shown to be disproportionately concentrated in mayoral and gubernatorial election years. Increases in police are shown to substantially reduce violent crime, but have a smaller impact on property crime. The null hypothesis that the marginal social benefit of reduced crime equals the costs of hiring additional police cannot be rejected.

This paper measures the effect on the federal funds rate of an open-market operation. The paper deals with simultaneous-equations bias by developing a proxy for the errors the Federal Reserve makes in forecasting the extent to which Treasury operations will add or drain reserves available to private banks. These errors induce fluctuations in bank reserves which have measurable consequences for the federal funds rate. The paper estimates that a reduction in nonborrowed reserves of $30 million, if sustained for an entire 14-day reserve maintenance period, will cause the federal funds rate to rise by 10 basis points.

This paper develops a methodology for consistently estimating the relative weights in senator utility functions, despite the fact that senator ideologies are unobserved. The empirical results suggest that voter preferences are assigned only one quarter of the weight in senator utility functions. The national "party line" also has some influence, but the senator's own ideology is the primary determinant of roll-call voting patterns. These results cast doubt on the empirical relevance of the median voter theorem. Estimation of the model requires only roll-call voting data, making it widely applicable.

This paper develops a methodology for consistently estimating the relative weights in senator utility functions, despite the fact that senator ideologies are unobserved. The empirical results suggest that voter preferences are assigned only one quarter of the weight in senator utility functions. The national 'party line' also has some influence but the senator's own ideology is the primary determinant of roll-call voting patterns. These results cast doubt on the empirical relevance of the median voter theorem. Estimation of the model requires only roll-call voting data, making it widely applicable.