Wealth will determine environment both between countries and within countries; again, nowhere is the effect of wealth more apparent than in the United States. As ever, it is difficult to separate this factor from those of race or occupation.

The sociology of cancer has been the subject of intense research in the United States, where the risk of getting cancer was studied in relation to socio-economic status in the TIM National Cancer Survey (published in the early 1970s). Irrespective of age or geographical location, a higher cancer incidence was observed in people with low income, with a steady fall in incidence as income increased, and with the lowest incidence of all being found in those with high incomes. The difference was about 20 per cent between the lowest and the highest income groups but was not uniform between different cancer sites. In men, the low-income groups did particularly badly for cancer of the lung, stomach and oesophagus, probably reflecting more smoking and drinking in the lower-income groups. In women, cancer of the cervix was more frequent in lower-income groups but there were two important exceptions to the general trend, with cancer of the breast and cancer of the body of uterus being less frequent in the low-income groups (perhaps reflecting nutritional differences or differences in child-bearing and menstruation).