How 4.5 million Irish immigrants became 40 million Irish Americans: demographic and subjective aspects of the ethnic composition of white Americans

In 1980, the US Census contained a subjective question about ethnic identity. Natural increase, intermarriage, and subjective identification contribute to the current size of each ethnic group. Simulations for the British-, Irish-, German-, and Italian-origin populations show the interaction among time of arrival, overall fertility and mortality trends, and differential fertility in determining natural increase. The subjective identification with some ethnic groups, notably the Irish and Germans, exceeds what natural increase would imply, while identification with other ethnic groups falls short of what demographic processes would imply. Loglinear models of ethno-religious intermarriage show that religious diversity is an important factor in the diffusion of Irish and German identities, while the relative religious homogeneity of the British and Italians limits the diffusion of those identities. -Authors