And the global population scarcely budged, held in check by unchanged food supplies, as th  7  predicted by Thomas Malthus in the late 18 century. Not for nothing was this called the Malthusian era. Another example of this secular stagnation, a favourite of mine, is provided by plotting heights from excavated skeletons records. These are a diagnostic on levels of health and nutrition. Male skeleton heights were essentially unchanged, at 160-170cm, for at least 2,000 years prior to 1750. Humans grew neither physiologically nor financially. And neither, then, did the societies in which they lived. That makes the contrast with developments in the last quarter of the millennium all the more striking. From around 1750, GDP per head suddenly took off and has kept on rising ever since, growing by around 1.5% per year. The magic of compound interest means these growth rates have transformed people’s living standards. The time it takes for living standards to double has shrunk to less than 50 years. The impact on people’s well-being, financial and psychological, has been transformational. It has meant each generation has been around 50% better off than its predecessor. After 1750, generational progress suddenly became visible, children to parents to grandparents. Growth in living standards became a social norm, in a way never previously true in human history. Life’s travellator turned into an escalator. And not just for GDP. Broader metrics of well-being tell a similar tale.
Indeed, one of the key benefits of globalisation over the past several decades is that the freer flow of goods and services, people and capital, ideas and information, has served as a vehicle for the transmission and diffusion of new technologies across borders. Other things equal, this should have accelerated catch-up between countries operating at and inside the technological frontier. 65  Other things, however, have not been equal. Penetration rates of new technologies, once adopted, tell a different tale. They suggest that, over time, there has been a divergence between frontier and non-frontier countries. In other words, the intensity with which new technologies have been used has expanded more rapidly in frontier (especially Western) economies than in non-frontier (non-Western) ones. This will have retarded catch-up between the two blocs. It is a less encouraging story about the diffusion of innovation. With the intensive and extensive margins of diffusion pushing in opposite directions, which has won out? It seems to have been the forces of divergence: slower rates of penetration of new technologies have more than counter-balanced faster rates of adoption across countries. This has shown up in levels of productivity between frontier and non-frontier which, since around 1980, have if anything diverged. Chart 7 illustrates that. It compares levels of productivity across 44 countries since 1950 relative to the frontier country (the US). Convergence prior to 1980 has given way to divergence subsequently.