Marx's Hypotheses on the Length of the Working Day
检验马克思关于工作日长度统一的假设，发现19世纪工厂数据不支持该假设，反而更符合新古典经济学中工作时长因工人偏好而异的观点。
In order to argue that value depends exclusively on labor, Marx had to assume a uniform rate of surplus value (exploitation) across all industries. But if this rate of exploitation is the same everywhere, hours of work have also to be uniform. Marx accordingly insisted that this was so and quoted contemporary evidence in support. A close examination of his sources (nineteenth-century factory inspectors' reports) fails, however, to confirm his prediction. Instead the data are more consistent with the competing neoclassical hypothesis, originating with Jevons, that work hours will vary because workers' labor and leisure preferences vary.