This article tests whether the correlation between wages and concentration of employment can be explained by unobserved worker productivity. Residential location is used as a proxy for unobserved productivity, and average commute time to workplace is used to test whether location-based productivity differences are compensated away by longer commutes. Analyses using confidential data from the 2000 Decennial Census find that estimates of agglomeration wage premia within metropolitan areas are robust to comparisons within residential location and that estimates do not persist after controlling for commuting costs, suggesting that the productivity differences across locations are due to location, not individual unobservables.

This paper develops a new approach for measuring the stringency of a major form of land use regulation, building height restrictions, and applies it to an extraordinary data set of land-lease transactions from China. Our theory shows that the elasticity of land price with respect to the floor area ratio (FAR), a building height indicator, is a measure of the regulation's stringency (the extent to which FAR is kept below the free-market level). Using a national sample, estimation allowing this elasticity to be city-specific shows variation in the stringency of FAR regulation across Chinese cities. Single-city estimation for Beijing shows that stringency varies with site characteristics.