The paper attempts to empirically quantify the factors underlying sigma convergence among the contiguous states of the U.S. Using annual state data the study finds a significant effect of the wedge in explaining the variation in state per capita productivity. Employing a time series framework, the paper finds that an increase in the variation of 1 percent in the wedge will increase the variation in per capita productivity by roughly 0.12 percent in the short run and roughly 0.45 to 0.55 percent in the long run.