In his analysis of the Maddison data, William Baumol (1986) found that poorer countries like Japan and Italy substarltially closed the per capita income gap with richer countries like the United States and Canada in the years from
1870 to 1979. Two objections to his analysis soon became apparent. First, in the Maddison data set, convergence takes place only in the years since World War 11. Between 1870 and 1950, income per capita tended to diverge (Abrarnovitz, 1986). Second, the Maddison data set included only those economies that had successfully industrialized by the end of the sample period. This induces a sample selection bias that apparently accounts for most of the evidence in favor of convergence (De Long, 1988).