Most empirical studies on states’ personnel contributions to UN peacekeeping operations (PKOs) use a state’s annual contributions as the unit of analysis. A critical problem of the state-level analysis is that it ignores the fact that states have to decide how to distribute these peacekeepers among more than a dozen peacekeeping missions. Ignoring the mission-level decision misses a significant part of states’ UN PKO contributions and could bias our empirical analysis. We propose a two-level model that sees a state’s UN PKO contributions as the interactions between the state-level and mission-level factors. This model is employed to revisit the heatedly debated “reimbursement hypothesis”. Our analysis of the empirical data between 1990 and 2018 shows a mixed relationship between states’ economic development and their UN PKO contributions. We also find that middle-income rather than low-income countries are the most critical providers of UN PKOs since the end of the cold war.

大多数关于国家对联合国维和行动（PKO）人员贡献的实证研究都以国家的年度贡献作为分析单位。国家层面分析的一个关键问题是它忽略了国家必须决定如何将这些维和人员分配给十几个维和特派团的事实。忽略任务级别的决定会错过各国对联合国维和行动的很大一部分贡献，并可能使我们的实证分析产生偏差。我们提出了一个两级模型，将一个国家对联合国维和行动的贡献视为国家级和任务级因素之间的相互作用。这个模型被用来重新审视激烈争论的“报销假说”。我们对 1990 年至 2018 年间经验数据的分析表明，各国的经济发展与其对联合国维和行动的贡献之间存在混合关系。