In this article we measure, describe, and demonstrate the importance of differential treatment for developing countries in multilateral environmental agreements (MEAs). So far, we argue, quantitative research on differentiation has been minimal due to data constraints and the complex nature of relevant provisions. In response, we offer a way of relieving this constraint, exploiting the fact that MEAs with differentiation typically identify distinct sets of “developing country” parties. After describing the data collection process, we show that differentiation is surprisingly uncommon, appearing in only 6 percent of MEAs, and disproportionately appears in larger, more recent agreements. We then test a key conjecture about differentiation by revisiting the debate on the depth–participation dilemma. We demonstrate, specifically, how it conditions this relationship. When MEAs do not differentiate, greater depth reduces participation; when they do, the relationship is reversed, making it possible to sustain high levels of both. This result helps to reconcile conflicting findings in earlier studies and has important policy implications.

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Author notes


Deborah Barros Leal Farias’s research was supported by the University of New South Wales. Charles Roger’s research was supported by the Institut Barcelona d’Estudis Internacionals and the Beatriu de Pinós Programme (2018 BP 00276, AGAUR, Generalitat de Catalunya). For their helpful comments and suggestions, we thank Jen Iris Allan, Peter Dauvergne, Yannis Karagiannis, Jean-Frédéric Morin, Miriam Prys-Hansen, Sam Rowan, the GEP editors, and the three anonymous reviewers. We also wish to thank Helmut Breitmeier and Ronald Mitchell for providing assistance with their data.

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