Detecting Technological Catch-Up in Economic Convergence

We address the problem of measuring, in the absence of reliable indexes of technology levels, how much of the convergence we observe is due to convergence in technology or in capital-labour ratios. We first develop a growth model where technology accumulation in lagging economies depends on their propensity to innovate and on technological spillovers, with convergence due both to capital-deepening and to technological diffusion. Then we study the transitional dynamics of the model to show how to discriminate empirically among the following three hypotheses: (i) convergence is due to capital-deepening with technology levels uniform across economies, as in Mankiw, Romer and Weil (1992); (ii) convergence is due to capital-deepening with stationary differences in individual technologies, as in Islam (1995); (iii) convergence is due to both technological catch-up and capital-deepening. Our main findings are as follows. First, we show that it may be difficult to distinguish between hypotheses (ii) and (iii) in cross-section or panel data. This problem has often been overlooked in the empirical literature on convergence. Second, we suggest how the problem can be overcome by noting that hypothesis (iii) does (and hypothesis (ii) does not) imply that the initial differences in technology levels may tend to decrease over time. A careful analysis of the fixed-effects estimates obtained by means of panel data methodology proposed in Islam (1995) should allow researchers to discriminate between the two competing hypothesis