Joint with Lauren Hoehn-Velasco and Amanda Wahlers
Milk was a major disease vector in the early twentieth century, yet the population-level effects of milk safety reforms remain poorly understood. In this paper, we examine the rollout of pasteurization ordinances across U.S. cities and show that pasteurization led to large, sustained improvements in public health. City-level event studies indicate that these ordinances reduced milkborne mortality by 16\%, averting approximately 800–1,200 deaths annually. Pasteurization specifically cut typhoid morbidity and mortality by 32-34\%, with the largest gains among older children and adults. These declines in milkborne mortality highlight pasteurization as a crucial yet undervalued driver of early 20th-century mortality declines.