and

In a model on population and endogenous technological change, Kremer (1993) combines a short-run Malthusian scenario where the level of income determines the population that can be sustained, with the Boserupian insight that, in the long run, greater population spurs technological change and can therefore lift a country out of its Malthusian trap. We extend this model and show that a more realistic version of the model, which combines population and population density, allows deeper insights into these processes. This model involves the explicit consideration of population density as an additional factor determining technological change. The incorporation of population density, which is closer to Boserup’s insight of demand-driven technological change and is more consistent with theories of technological diffusion, allows a superior interpretation of the empirical regularities between the level of population, population density, and population growth. Our model is also consistent with findings about technological change in different regions of the world which cannot easily be accommodated in Kremer’s original framework. Acknowledgements We would like to thank Michael Kremer, participants at a research seminar at the University of Munich as well as at participants of a session at the 2001 EEA conference in Lausanne for helpful comments and suggestions. 1 1