Contract duration and relationship-specific investments: Empirical evidence from coal markets
利用277份煤炭合同数据，实证检验了关系专用投资对合同期限的影响，发现当关系专用投资更重要时，买卖双方会在合同执行阶段做出更长期的承诺。
This paper examines empirically the importance of relationship investments in determining the duration of coal contracts negotiated between coal suppliers and electric utilities, using data for 277 coal contracts. For each contract, measures of the duration of contractual commitments agreed to by the parties at the contract execution stage and measures of the importance of relationship specific investments are developed. The results provide strong support for the view that buyers and sellers make longer commitments to the terms of future trade at the contract execution stage, and rely less on repeated bargaining, when relationship-specific investments are more important. Copyright 1987 by American Economic Association.