Military enlistment is highly selective for reasons of both labor demand and supply. An early-twentieth-century evolution of military technology that shifted the demand for workers of different stature illustrates the importance of labor demand beyond the commonly discussed influences originating with labor supply. English-born soldiers in the Anglo-Boer War (1899–1902) were taller, on average, than those of World War I (1914–18), yet these differences cannot be attributed to standard of living or business cycle influences on the labor market. Rather, we argue, the mechanization and bureaucratization of warfare increased the relative value of shorter people permitting a decline in the average height of soldiers. Technological change over the period of these two wars affected labor demand in a way that must be recognized before using this evidence to test hypotheses about changes in population health.

中文翻译：

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军事技术和样本选择偏差

出于劳动力需求和供应的原因，入伍具有高度选择性。20 世纪初军事技术的发展改变了对不同身材工人的需求，这表明劳动力需求的重要性超出了通常讨论的源于劳动力供应的影响。平均而言，在盎格鲁-布尔战争（1899-1902 年）中出生的英国士兵比第一次世界大战（1914-18 年）中的士兵高，但这些差异不能归因于生活水平或商业周期对劳动力的影响市场。相反，我们认为，战争的机械化和官僚化增加了矮个子的相对价值，从而允许士兵的平均身高下降。