Sigma Convergence versus Beta Convergence: Evidence from U.S. County-Level Data

In this paper we outline (i) why sigma-convergence may not accompany beta-convergence, (ii) discuss evidence of beta-convergence in the U.S., and (iii) use U.S. county-level data containing over 3,000 cross-sectional observations to demonstrate that sigma-convergence cannot be detected at the county-level across the U.S., or within the large majority of the individual U.S. states considered separately. Indeed, in many cases statistically significant sigma-divergence is found.