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.
