On the Long Term Effects of the 1918 U.S. Influenza Pandemic

Pioneering work by Douglas Almond (2006) used the 1918 Spanish influenza pandemic to establish that in utero exposure to health insults has a large, negative impact on health and socioeconomic prosperity that reaches well into adulthood. A key assumption underlying this body of research is that in utero exposure to the influenza pandemic can be treated as if it were randomly assigned. The validity of that assumption is investigated using data from the 1920 and 1930 U.S. Censuses. We find that those who were exposed in utero were born to families of lower socioeconomic status relative to the cohorts who were not exposed. Specifically, fathers of the exposed cohort made significantly less income, had lower socioeconomic status, were older, had higher fertility, were less likely to be white, and were less likely to be WWI veterans than the fathers of those who were not exposed in utero. When including controls for childhood environment, the effect of in utero exposure on adult outcomes becomes small in magnitude and not statistically significant. Conclusions about the deleterious impact of in utero exposure to the influenza pandemic on socioeconomic prosperity in adulthood are, at best, premature.