When Archie Cochrane, Fred Moore and I conceived of trying to relate mortality in developed countries to measures of health service provision little did we imagine that it would set a hare running 20 years into the future.1 To us this was an amusing correlational study in the spirit of McKeown2 and Illich3—those sceptics of medical prowess. That our work has been reprinted in two collections of epidemiological papers and also as a historical article in this journal is surprising. It is surprising because correlational studies such as these (known nowadays as ecological studies) are at the, despised, bottom of the currently fashionable hierarchy of evidence promulgated, ironically, by the Cochrane Collaboration among others.

The hare was not that a statistical association between health service provision and mortality was absent. Rather it was the marked positive correlation between the prevalence of doctors and infant mortality. Whatever way we looked at our data we could not make that association disappear. Moreover, we could identify no plausible mechanism that would give rise to this association. We were willing to accept that doctors have negligible beneficial impact on mortality rates and …