Optimal Contracts with Lock-In
分析当买方投入关系专用性启动成本、卖方选择第三方不可验证的质量时，不完全长期合同如何实现最优。若启动成本可观察，短期合同即可达到最优；若不可观察，长期价格合同优于短期合同，但均衡可能低质量或无转换，税收转换或第三方介入可改善福利。
The authors analyze incomplete long-term contracts when buyers incur relationship-specific set-up costs and sellers choose product or service quality that is not verifiable to third parties. If set-up costs are observable, the first-best outcome can be achieved even though contracts cannot enforceably specify quality; this does not even require long-term contracts. If set-up costs are unobservable, however, then long-term price contracts can strictly outperform short-term contracts. Equilibrium may involve either inefficiently low quality with no buyer switching or efficient quality with inefficient switching. A policy of taxing switching, or the availability of "budget-breaking" third parties, can improve welfare. Copyright 1989 by American Economic Association.