This paper explores a possible sampling bias in field experiments through a unique combination of a large-scale field experiment on ethnic discrimination in the German rental housing market (N = 2,992 tested apartments) and data on the internet housing market where the apartments were sampled from (observation of the whole platform for about one year). Up to now, most field experiments sampled on the level of suppliers (not apartments) and selected the tested suppliers within a short field period (point sampling). This probably led to an over-representation of small suppliers and apartments that had already been advertised for a long time, resulting in an under-representation of large suppliers and new vacancies. We analyze how both issues affect the measurement of ethnic discrimination and its underlying mechanisms. With our case study on the German housing market, we first observed the expected sampling bias: There was a strong over-sampling of small suppliers and apartments already offered for a long time. Second, this bias was found to have only little impact on the descriptive result of substantial discrimination against Turkish applicants. There was only a slight tendency that discrimination was higher for small suppliers and offers advertised for a relatively short time (i.e. new vacancies). Overall, we conclude that evidence on ethnic discrimination and its underlying risk factors is remarkably robust to the used sampling technique. Although there were no indications of a severe bias, our market data illustrate opportunities to test the effects of market conditions that often remained unnoticed.

本文通过对德国租赁住房市场中种族歧视的大规模实地实验的独特组合，探索了实地实验中可能存在的抽样偏差（N = 2,992个经过测试的公寓）和有关从中采样公寓的互联网住房市场的数据（观察整个平台大约一年）。到目前为止，大多数现场实验都是在供应商（而非公寓）的水平上进行采样的，并在较短的现场时间内选择了经过测试的供应商（点采样）。这可能导致长期以来已经做广告的小型供应商和公寓的人数过多，导致大型供应商的人数不足和新的职位空缺。我们分析了这两个问题如何影响对种族歧视及其潜在机制的衡量。通过我们对德国住房市场的案例研究，我们首先观察到了预期的抽样偏差：长期以来，小型供应商和公寓的供过于求。第二，人们发现这种偏见对对土耳其申请人的实质性歧视的描述结果影响很小。仅有很小的趋势，即对小型供应商的歧视较高，而在较短时间内广告的要约（即新的职位空缺）。总体而言，我们得出结论，关于种族歧视及其潜在风险因素的证据对于所使用的采样技术非常可靠。尽管没有迹象表明存在严重的偏差，但我们的市场数据显示出了检验市场状况影响的机会，而这些状况往往未被人们注意到。新的职位空缺）。总体而言，我们得出结论，关于种族歧视及其潜在风险因素的证据对于所使用的采样技术非常可靠。尽管没有迹象表明存在严重的偏差，但我们的市场数据显示出了检验市场状况影响的机会，而这些状况往往未被人们注意到。新的职位空缺）。总体而言，我们得出结论，关于种族歧视及其潜在风险因素的证据对于所使用的采样技术非常可靠。尽管没有迹象表明存在严重的偏差，但我们的市场数据显示出了检验市场状况影响的机会，而这些状况往往未被人们注意到。