Abstract It is well recognized that consistent estimation of peer effects faces formidable identification challenges. The confounding factors the literature usually focuses on are endogenous group formation, correlated unobservables and simultaneity. In this paper, I show that another significant source of bias arises when a researcher examines peer effects in product adoption. When people differ in their valuations of a product, people with higher valuations tend to adopt earlier so that only those with increasingly lower valuations comprise the set of potential adopters as time progresses. Such an endogenous attrition over time, if not correctly accounted for, will lead to inconsistent estimates of peer effects. I present simulations to numerically demonstrate the presence and extent of such a selection bias. I also propose a simple solution to remove the bias and examine its performance.

中文翻译：

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选择偏差估计产品采用的同伴效应

摘要众所周知，对同伴效应的一致估计面临着巨大的识别挑战。文献通常关注的混杂因素是内源性群体形成，相关的不可观察性和同时性。在本文中，我表明，当研究人员研究产品采用过程中的同伴效应时，会产生另一个明显的偏见。当人们对产品的估价有所不同时，具有较高估价的人往往会更早采用，因此随着时间的推移，只有具有较低估价的人才构成潜在采用者的集合。如果没有正确解释，随着时间的流逝，这种内生性损耗会导致对同伴效应的估计不一致。我提出了一些模拟，以数值方式证明了这种选择偏差的存在和程度。