Wilkinson1 and Lynch et al 2 produce widely differing estimates of the relation between absolute income and life expectancy in developed, or more affluent, societies. Both analyse data for 1993. Wilkinson3 focuses on “developed” societies and reports a correlation of 0.08 based on 23 OECD countries. Lynchet al focus on levels of affluence and after adding 10 “equally wealthy” countries report a correlation of 0.51.

They also point out that GDP and life expectancy estimates vary according to the data source. It follows that part of the discrepancy between the two findings could be due to having used different sources.

To quantify this I have attempted to reproduce both analyses from a single data source: the World Bank Development Indicators CD-ROM (1999). Lynch et al used the 1997 version, but the GDP data for 1993 seem identical in the later version. Life expectancy data were also drawn from the same source, whereas Lynchet al used the WHO web site. Where data were not available for 1993, they were estimated by linear interpolation from the nearest two years before and after. This leads to slightly different estimates of life expectancy, but should not materially affect the results here.

Two further points are worth mentioning. Firstly, Lynchet al include 33 countries with GDP per capita over $10 000, whereas there are 34 such countries in this dataset. Apparently, Hong Kong was omitted from the earlier version. It has been included here, in keeping with the logic of including all equally wealthy countries. Secondly, in 1993 the OECD comprised 24 member states.4 Turkey, which ranked 57 in terms of GDP per capita at $5550, has been excluded.

Among the 34 states with GDP over $10 000 the correlation with life expectancy is 0.47, slightly lower than that reported by …

(R.G.Wilkinson{at}sussex.ac.uk)

Dr Lynch (jwlynch{at}sph.umich.edu)

Dr Lynch (jwlynch{at}sph.umich.edu)

Dr Lynch (jwlynch{at}sph.umich.edu)

Dr Lynch (jwlynch{at}sph.umich.edu)