Behavioral Responses and the Impact of New Agricultural Technologies: Evidence from a Double‐blind Field Experiment in Tanzania
在坦桑尼亚农村进行常规和双盲随机试验，发现农民知道获得现代种子后会付出更多努力，导致传统经济试验高估技术效果，实际收成与不知情者无差异。
Randomized controlled trials (RCTs) in the social sciences are typically not double‐blind, so participants know they are “treated” and will adjust their behavior accordingly. Such effort responses complicate the assessment of impact. To gauge the potential magnitude of effort responses we implement a conventional RCT and double‐blind trial in rural Tanzania, and randomly allocate modern and traditional cowpea seed varieties to a sample of farmers. Effort responses can be quantitatively important—for our case they explain the entire “treatment effect on the treated” as measured in a conventional economic RCT. Specifically, harvests are the same for people who know they received the modern seeds and for people who did not know what type of seeds they got; however, people who knew they had received the traditional seeds did much worse. Importantly, we also find that most of the behavioral response is unobserved by the analyst, or at least not readily captured using coarse, standard controls.