Interpreting Experimental Evidence in the Presence of Postrandomization Events: A Reassessment of the Self-Sufficiency Project
重新评估了自给自足项目（SSP）的实验证据，发现政策变化导致对照组行为不具可比性，修正后激励效果显著不同，提醒解读实验结论需谨慎。
The Self-Sufficiency Project (SSP) was a well-known welfare-to-work experiment that provided a generous but time-limited financial incentive to leave welfare and enter the workforce. Experimental evidence showed large short-term impacts but no lasting effects. We argue that these conclusions need to be reassessed. Policy changes implemented during the SSP implied that the control group’s behavior did not provide an appropriate counterfactual. We estimate the impacts the financial incentive would have had in an unchanging policy environment. This reassessment leads to significant changes in the lessons previously reached. Our study demonstrates that experimental findings need to be interpreted with care.