The potential welfare benefits of unemployment insurance, along with the optimal replacement ratio, are studied using a quantitative dynamic general equilibrium model. To provide a role for unemployment insurance, agents in our economy face exogenous idiosyncratic employment shocks and are unable to borrow or insure themselves through private markets. In the absence of moral hazard, replacement ratios as high as .65 are optimal and the welfare benefits of unemployment insurance are quite large. However, if there is moral hazard and the replacement ratio is not set optimally, but is instead set to an empirically plausible value, the economy can be much worse off than it would be without unemployment insurance.

The potential welfare benefits of unemployment insurance, along with the optimal replacement ratio, are studied using a quantitative dynamic general equilibrium model. To provide a role for unemployment insurance, agents in our economy face exogenous idiosyncratic employment shocks and are unable to borrow or insure themselves through private markets. In the absence of moral hazard, replacement ratios as high as .65 are optimal and the welfare benefits of unemployment insurance are quite large. However, if there is moral hazard and the replacement ratio is not set optimally, but is instead set to an empirically plausible value, the economy can be much worse off than it would be without unemployment insurance.

Recent theories of economic growth, including those of P. Romer (1986, 1990), M. Porter (1990), and J. Jacobs (1969, 1984), have stressed the role of technological spillovers in generating growth. Because such knowledge spillovers are particularly effective in cities, where communication between people is more extensive, data on the growth of industries in different cities allow the authors to test some of these theories. Using a new data set on the growth of large industries in 170 U.S. cities between 1956 and 1987, they find that local competition and urban variety, but not regional specialization, encourage employment growth in industries. The evidence suggests that important knowledge spillovers might occur between rather than within industries.

Recent theories of economic growth, including those of Romer, Porter, and Jacobs, have stressed the role of technological spillovers in generating growth. Because such knowledge spillovers are particularly effective in cities, where communication between people is more extensive, data on the growth of industries in different cities allow us to test some of these theories. Using a new data set on the growth of large industries in 170 U.S. cities between 1956 and 1987, we find that local competition and urban variety, but not regional specialization, encourage employment growth in industries. The evidence suggests that important knowledge spillovers might occur between rather than within industries, consistent with the theories of Jacobs.