Long-term outcomes of experimental evaluations are necessarily observed after long delays. We develop semiparametric methods for combining the short-term outcomes of experiments with observational measurements of short-term and long-term outcomes, in order to estimate long-term treatment effects. We characterize semiparametric efficiency bounds for various instances of this problem. These calculations facilitate the construction of several estimators. We analyze the finite-sample performance of these estimators with a simulation calibrated to data from an evaluation of the long-term effects of a poverty alleviation program.

翻译：实验评估的长期结果必然需要长时间延迟才能观测到。我们开发了将实验的短期结果与观测性短期和长期结果数据相结合的半参数方法，以估计长期治疗效应。我们针对该问题的多种情形刻画了半参数效率界，这些计算促进了若干估计量的构造。通过模拟实验分析了这些估计量的有限样本表现，该模拟基于一项扶贫项目长期效应评估的实际数据进行了校准。