Commentary: Preston and mortality trends since the mid-1970s

Preston’s classic 1975 paper1 appeared at a point when life-expectancy in most countries of the world had been increasing for a considerable period. The aim of the paper was to explore the explanations for these improvements. Particular attention was given to the relative contribution of economic factors as measured by national income per head of population. His key conclusion was that less than half of the improvements observed between the 1930s and 1960s could be attributed to such economic factors. Moreover, contrary to what had been assumed, improvements in nutrition and education appeared to have had only a small role. Instead, Preston concluded that considerably more than half of the increase in life expectancy was a result of the positive influence of the global diffusion of medical and health technologies. These ‘exogenous factors ’ included innovations in hygiene an