Revising Infant Mortality Rates for the Early 20th Century United States

Accurate vital statistics are required to understand the evolution of racial disparities in infant health and the causes of rapid secular decline in infant mortality during the early twentieth century. Unfortunately, infant mortality rates prior to 1950 suffer from an upward bias stemming from a severe underregistration of births. At one extreme, African-American births in Southern states went unregistered at the rate of 15 to 25 percent. In this paper, we construct improved estimates of births and infant mortality in the United States for the 1915-1940 period using recently released complete count decennial census microdata combined with the counts of infant deaths from published sources. We check the veracity of our estimates with a major birth registration study completed in conjunction with the 1940 Decennial Census, and that the largest adjustments occur in states with less complete birth registration systems. An additional advantage of our census-based estimation method is the extension back of the birth and infant mortality series for years prior to published estimates of registered births, enabling previously impossible comparisons and estimations. Finally, we show that underregistration can bias effect estimates even in a panel setting with specifications that include location fixed effects and place-specific linear time trends.