Studies of NATO rely heavily on military spending as a fraction of GDP as the key indicator of members’ contribution to the alliance, but a growing number of scholars have challenged this approach. We suggest that each member’s public goods provision is a better measure of commitment to the alliance. In the case of post-Cold War NATO, out-of-area troop deployments (adjusted for population) constitute one of the strongest indicators of a state’s contribution to public goods. Providing troops for NATO missions in Afghanistan, Kosovo, and Bosnia-Herzegovina is one of the clearest signals of high commitment to the alliance. Using deployment data from 2004 to 2018, we show that there is evidence of disproportionate burden-sharing within the alliance. Countries like Slovenia, Denmark, the USA and UK contributed far more to NATO deployments than others like Turkey, Spain, Poland, and Portugal. We also use the data to begin examining possible causes of these disparities. We find that wealthier countries, countries that spend more on their militaries, and newer alliance members are more likely to contribute. Our indicator and first-cut model open avenues for further research on why some members demonstrate higher commitment to NATO than others.

北约的研究严重依赖军事支出占国内生产总值的一小部分，作为成员对联盟所作贡献的关键指标，但是越来越多的学者对这种方法提出了挑战。我们建议，每个成员提供的公共物品都可以更好地衡量对联盟的承诺。就冷战后的北约而言，区域外部队的部署（根据人口调整）是国家对公共产品贡献最大的最强指标之一。为北约在阿富汗，科索沃和波斯尼亚和黑塞哥维那的特派团提供部队是对联盟高度承诺的最明显信号之一。使用2004年至2018年的部署数据，我们发现有证据表明联盟内部的负担分担不成比例。斯洛文尼亚，丹麦，美国和英国对北约部署的贡献远超过土耳其，西班牙，波兰和葡萄牙。我们还使用数据开始检查这些差异的可能原因。我们发现，较富裕的国家，在军事上花费更多的国家以及较新的联盟成员更有可能作出贡献。我们的指标和第一手模式为进一步研究某些成员为何表现出比其他成员表现出更高的北约承诺开辟了道路。