The convergence hypothesis has generated a huge empirical literature: this paper critically reviews some of the earlier key ndings, claries their implications, and relates them to more recent results. Particular atten- tion is devoted to interpreting convergence empirics. The main ndings are: (1) The much-heralded uniform 2% rate of convergence could arise for reasons unrelated to the dynamics of economic growth. (2) Usual empirical analyses|cross-section (conditional) convergence regressions, time series modelling, panel data analysis|can be misleading for under- standing convergence; a model of polarization in economic growth clarifies those difficultles. (3) The data, more revealingly modelled, show persis- tence and immobility across countries: some evidence supports Baumol's idea of \convergence clubs"; some evidence shows the poor getting poorer, and the rich richer, with the middle class vanishing. (4) Convergence, un- ambiguous up to sampling error, is observed across US states.
