We organize a real‐effort field experiment with varying piece rates to assess the impact of wages and social comparisons on productivity. In addition to analyzing how piece rates and social comparisons affect productivity during the ‘paid stage’ of the experiment, we also consider how they affect effort supply during a voluntary and unpaid follow‐up task. Our main results are that effort supply is relatively unresponsive to variation in own earnings, but responds strongly to pay inequality. While we obtain weak support for the hypothesis that positive social comparisons invite extra effort during paid stages of the experiment, our most important finding is that social comparisons matter for voluntary tasks when shirking is cheap. Specifically, positive social comparisons positively affect productivity during unpaid tasks, and negative comparisons have the opposite impact.

中文翻译：

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工资差异和工人的努力：来自乌干达的实验证据

我们组织了一项不同计件费率的实际努力现场实验，以评估工资和社会比较对生产力的影响。除了分析计件工资和社会比较在实验的“有偿阶段”期间如何影响生产力之外，我们还考虑了它们如何影响自愿和无偿后续任务期间的努力供给。我们的主要结果是，努力供给对自己收入的变化相对没有反应，但对薪酬不平等反应强烈。虽然我们对积极的社会比较在实验的付费阶段会带来额外努力的假设获得了微弱的支持，但我们最重要的发现是，当逃避成本低时，社会比较对自愿任务很重要。具体而言，积极的社会比较对无偿任务期间的生产力产生积极影响，