Sigma convergence versus beta convergence: Evidence from US 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 United States, 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 United States, or within the large majority of the individual U.S. states considered separately. Indeed, in many cases statistically significant sigma-divergence is found.