Early Dairy Regulation: Raw Milk Laws and Child Mortality in the United States

This study examines the public health impact of early dairy regulation in the United States by analyzing the relationship between raw milk laws and child mortality from 1850 to 1950. Using linked census microdata from the Integrated Public Use Microdata Series (IPUMS) full-count datasets, intercensal child mortality rates are constructed for children aged 0-5, and a staggered adoption difference-in-differences design is employed to estimate the causal effects of dairy regulations. The identification strategy exploits the heterogeneous timing of raw milk law adoption across counties, with regulations emerging in 1914. The analysis tracks approximately 54.8 million children across ten decade pairs, focusing on families with successfully linked parents to minimize measurement error in mortality estimation. Results indicate that comprehensive dairy regulations did not, on average, reduce child mortality. The preferred specification restricts estimation to individually-verified municipal ordinance counties, the jurisdictions where mandates were most plausibly binding, and is the only specification satisfying the parallel trends assumption. Remaining specifications fail the parallel trends test, consistent with positive selection of urbanizing, lower-mortality counties into treatment. The null result is consistent with voluntary pre-adoption, weak enforcement outside major cities, and declining milk-borne exposure as concurrent water infrastructure improvements reduced competing causes of child death.