"Human capital-based theories of cities suggest that large, economically diverse urban agglomerations increase worker productivity by increasing the rate at which individuals acquire skills. One largely unexplored implication of this theory is that workers in big cities should see faster growth...

"In finding a career, workers tend to make numerous job changes, with the majority of 'complex' changes (i.e. those involving changes of industry) occurring relatively early in their working lives. This pattern suggests that workers tend to experiment with different types of work before settling...

"Through their influence on the cross-sectional distribution of productivity across firms and workers, job creation and destruction likely have an impact on the rate at which aggregate productivity changes over time. However, the nature of this effect is not, a priori, clear. While a broad...