By the end of the First World War, in most of the United States, when a worker had an accident, employers were legally required to provide compensation for medical care and lost work. For employers, this was a massive shift in their economic calculus. Work accidents once cost only as much as replacing a worker. Now the only way for an employer to reduce costs was to reduce accidents. The decline in work accidents was dramatic. Over the next two decades, deaths per hour worked would fall by two-thirds. At U.S. Steel, in the first decade of the 1900s, one in four workers suffered significant injuries every year. By the late 1930s, that number was one in three hundred.
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