ECARES (Université Libre de Bruxelles - SBS-EM) and CEPR, Belgium.
University of Southampton, United Kingdom.
J Health Econ. 2019 Dec;68:102243. doi: 10.1016/j.jhealeco.2019.102243. Epub 2019 Oct 1.
Generic drugs are sold at a fraction of the original brand price. Yet, generic entry typically produces a drop in the quantity market share of the molecule losing exclusivity. This effect is economically and statistically significant for a large dataset covering hundreds of prescription drugs sold in the US during the period 1994Q1-2003Q4. This paper proposes the first systematic analysis of what appears to be a market anomaly. We propose a model to characterize the market equilibrium before and after generic entry. We identify precise conditions under which entry reduces the quantity market share of the molecule. Intriguingly, this is more likely to occur when the remaining patent-protected molecules feature low horizontal differentiation. We test this and other theoretical predictions of the model and find they are validated empirically.
仿制药的售价仅为原品牌药品的一小部分。然而，仿制药的进入通常会导致失去专利保护的药品的市场份额下降。对于涵盖 1994 年第一季度至 2003 年第四季度期间在美国销售的数百种处方药的大型数据集，这种效应在经济和统计学上是显著的。本文首次对这一似乎是市场异常的现象进行了系统分析。我们提出了一个模型来描述仿制药进入前后的市场均衡。我们确定了在何种情况下进入会降低药品的市场份额。有趣的是，当剩余的受专利保护的药品具有较低的水平差异化时，这种情况更有可能发生。我们对该模型的其他理论预测进行了测试，发现这些预测在经验上是有效的。
