1.3. The Analyses of Convergence

The panel data on top incomes is used here to address the question of convergence of the United States over the past century. Did the richest states experience slow rates of growth while the poorest states recorded fast rates of growth, with both ends eventually converging to a common average? Does the same conclusion hold when it comes to considering top incomes instead of average incomes? If true, how does it impact inequality across states? Furthermore, convergence can be approached in terms of income dispersion. What conclusions can be drawn from the comparison between the dispersion of average income and the dispersion of top income? Finally, another aspect of convergence raises the issue of the estimation of the income distribution itself, as it has been only partially known so far. Suppose that we can derive, one way or another, all deciles of the spectrum. In that case, we would be able to address the following question. To which extent does top decile converge towards or diverge away from the lower deciles of the income distribution? How did one evolve with respect to the other over time?