1.2. A Double-Contradiction Rekindles the Debate

The starting point of this study is a contradiction that emerges from two currents of the literature: the income inequality literature, and the regional convergence literature. On income inequality, the natural decrease of inequality predicted by Kuznets (1955) does not rally strong empirical support. On regional convergence, neo-classical economists support convergence whereas geographers marshal evidence for divergence, at least in the case of the United States at the sub-national level.

What can possibly be added to the long-standing debate on regional income inequality? This thesis sheds light on the subject through the construction and use of a new panel data set of 4,641 income inequality observations (the 50 U.S. states plus the District of Columbia over 91 years from 1913 to 2003). Various inequality indicators are derived from this database. At the national level, the time-series data here are very similar to those of Piketty and Saez (2004) . At the state level, there is no possible comparison with Piketty and Saez’s series as their data set does not allow for sub-national differentiation. Many empirical studies used panel data on income inequality within the United States, but none, to my knowledge, covers such a comprehensive range of years for each state.