The determinants of the health of whole populations has been largely the province of social epidemiologists rather than that of economists. The empirical difficulties are formidable. The determinants are many and they stretch back in time through genetic inheritance and parental child-rearing. The causal pathways through social conditions have their impacts on health, some of which seem to operate via stresses on the human immune system, are only beginning to be understood and there is much to uncover in this inherently multidisciplinary territory. A notable group has been those working with Michael Marmot at University College London (e.g. Marmot et al., 1991). Those working with Robert Evans in the (now completed) Canadian Institute for Advanced Research's Population Health Program included several economists besides Evans himself (e.g. Evans et al., 1994, Heymann et al., 2006). The many interna tional studies led by Wagstaff and Van Doorslaer are the main economic contributions in the fields of equity of health care, health care financing and health itself in both the developed world and the developing (e.g. Wagstaff and Van Doorslaer, 2000). Some recent econometric work tends to overturn common presumptions amongst epidemiologists - with respect, for example, to the impact of lifestyle on mortality.
Another usage is more strictly epidemiological and distinguishes the causes of cases from the causes of incidence, with population health being concerned with the latter and population health interventions being those aimed at shifting the distribution of disease rather than compressing its tails.