The evolution of contracting: evidence from the US freight rail industry
利用美国货运铁路行业现货市场与合同运输的数据库，研究了经济主体何时以及如何采用合同，以及合同倾向如何随时间演变，发现立法变化、合同经验、竞争程度、交易复杂性、资产专用性和技术变革等因素驱动了这一演进。
Abstract Although they lie at the very foundation of economic exchange, the primal questions of whether and when economic actors employ contracts and how the propensity to contract evolves over time have received relatively little empirical attention. We address these lacunas using an extensive database of spot market and contract shipments in the US freight rail industry. We find that the evolution of contracting is driven by many factors, including legislative changes, contracting experience, the extent and nature of prevailing competition, transaction complexity, asset specificity, and technological change.