The invention of the actuarial risk factor was one of two major innovations required for the formulation of programs to promote healthier lifestyles. The other was the concept of educating the public that personal behaviors can affect health. The discovery that some lifestyles were healthier than others emerged from findings that nationality groups with similar incomes and living conditions varied widely in their total and infant mortality rates.

One of the major uses of vital statistics in the early twentieth century was to compare the health status of different population groups. Nationality groups were the most important groups in the northeastern and midwestern cities teeming with immigrants and their children. Federal, state, and local governments regularly gathered information on place of birth and the place of birth of both parents. Individuals were categorized as “native born,” “foreign born,” and “foreign stock” (native born with at least one foreign born parent).

Nationality groups were useful categories because they constituted genuine communities. They shared languages, neighborhoods, occupations, cultures, churches, and fraternal and mutual aid societies. Their members had high rates of marriage within the group. Group solidarity was strengthened by language barriers, discrimination, and mutual hostilities with other nationality groups.

The foreign born and their children were also considered the source of most social and health problems. In his 1870 book, The Dangerous Classes of New York, Charles Loring Brace, a pioneer in the social welfare movement, stated that “an immense proportion of our ignorant and criminal class are foreign born; and of the dangerous classes here, a very large part, though native-born, are of foreign parentage.”