History Dependence in Drug Demand: Identification and Implications for Entry Incentives
利用选择集的时间不连续性识别药物需求中的历史依赖，发现患者今天被随机分配一种药物后，四年后仍使用同种药物的概率增加54个百分点，且这种依赖影响制造商的进入时机激励。
Abstract I use temporal discontinuities in choice sets to identify history dependence in drug demand, finding large and long-term effects. Quasi-randomly assigning a patient to a drug today increases the probability she is taking the same drug four years later by 54 percentage points. History dependence is stronger in patients taking multiple medications and weaker in drugs that are significantly more effective than substitutes. It is also weaker in generics and line extensions, driven by switching from the reference branded drug. I use a pair-specific switching-cost model to capture these patterns and provide suggestive evidence that they affect manufacturers’ entry timing incentives.