题目：Veriability and Fraud in a Dynamic Credence Goods Market
摘要：Complementary to the existing literature that extensively studied credence goods markets in static settings, we develop a dynamic model in which a durable good breaks down stochastically after treatments, and the customer meets the expert recurrently. We assume that the minor treatment alleviates the symptom of the major problem but fails to cure it, increasing the future failure rate. In contrast to the literature, we show that the truth-telling equilibrium never exists under the verifiability assumption, because the standard equal-margin condition fails. In our dynamic setting, the expert has a stronger incentive to undertreat since undertreatment induces more future business. But on the other hand, the customer becomes less willing to pay for the minor treatment for fear of increased future payments. Therefore, depending on the relative magnitude of these two opposing forces, either undertreatment or overtreatment can emerge in equilibrium. Surprisingly, the expert's incentive to undertreat weakens as the increment of failure rates rises.