Smaller families, improved knowledge about nutrition and hygiene, and a cleaner environment with better housing, less overcrowding and a reduction in toxic heavy industry – all of these things have contributed to the spectacular increase in the height of the average young man in Britain over the past one hundred years.
An new IZA Discussion Paper by Roy Bailey (University of Essex), Tim Hatton (University of Essex and IZA) and Kris Inwood (University of Guelph) finds that a century ago the average height of British men was 168cm (5 feet 6 inches) compared with 178cm (5 feet 10 inches) today. In order to understand this we need to know why earlier generations were so short.
The two key ingredients of growth during childhood are nutrition, which builds bone and tissue, and disease, which impedes that process. These in turn depend on socio-economic conditions during childhood, which include household circumstances and conditions in the local area.
This study finds that household size mattered: men with six siblings were half an inch shorter than those with just one. But the locality mattered even more; men from districts where disease was rife were an inch shorter than those from the healthiest districts.
The researchers study the heights of men who were born in the 1890s and who enlisted in the British army in the First World War. Because of the pressures for ever more soldiers, recruitment was not very selective. Indeed, nearly one in every ten men in the sample were shorter than the official minimum height of five feet three inches. So they are fairly representative of their generation.
To capture their childhood circumstances, the study locates them as children in the 1901 census. By contrast with other historical studies of height (which typically capture only birthplace characteristics), the researchers are able to observe conditions in the individual’s childhood household as well as in the wider locality.
Analyzing the influence of household conditions, they find that recruits were shorter the more siblings they had, and surprisingly, the more earners there were in the family. The recruits were also shorter the more crowded the household and the lower the socioeconomic status of the household head. Thus, children growing up in larger, poorer and more crowded households had worse nutrition and were more exposed to infection.
But the strongest influence is the local disease environment, as measured by the infant mortality rate in the district. At the turn of the century, 15% of children died before their first birthday and so this is a sensitive indicator of the healthiness of different districts. Unhealthy districts were typically those where overcrowding was widespread, where heavy industry was prominent and where illiteracy was high (especially among mothers).
The results provide some clues as to what changed over the twentieth century. Public investment in water supply and sewage disposal was important in producing a cleaner environment. So was improvement in housing, as the slums were cleared and overcrowding was reduced. Heavy industry withered and became much less toxic.
And although access to better medical treatments expanded only modestly until after the Second World War, basic knowledge about nutrition and hygiene spread more and more widely. Advances in the education of parents (particularly mothers) combined with smaller families brought significant improvements in the nurturing of children.