Transitory versus Durable Boundary Crossing: What Explains the Indigenous Population Boom in Mexico? 1 René D. Flores Regina Martínez Casas University of Chicago Centro de Investigaciones y Estudios Superiores en Antropología Social María Vignau Loría University of Washington Ethnic boundary crossing takes two different forms that have distinct triggers, traits, and potential outcomes: transitory crossing, which is typ- ically short-term, reversible, and triggered by microcontextual cues, and durable crossing, which is a longer-lasting, gradual process motivated by macropolitical forces such as social movements and government pol- icies. This theoretical distinction helps explain the unexpected growth in the long stigmatized self-identified indigenous population in Mexico, which has tripled since 2000. Using a demographic projection model, the authors find that natural demographic processes contributed little to this sudden growth. Instead, using experimental and census data, they find that transitory crossing into the indigenous category was acti- vated by phrasing changes to the 2010 census identification question. The authors theorize that durable crossing is being simultaneously acti- vated by the growing salience of the indigenous movement and the Mex- ican government’s embrace of multiculturalism. These political factors appear to be shaping the social meaning of indigeneity itself. INTRODUCTION As indigenous languages decline throughout Latin America, local govern- ments are increasingly relying on self-identification to capture indigenous 1 We thank Andrew Abbott, Charles Hirschman, Ariela Schachter, Stewart Tolnay, and Ilana Ventura for their helpful suggestions and valuable comments. We also thank Pablo © 2023 The University of Chicago. All rights reserved. Published by The University of Chicago Press. https://doi.org/10.1086/725337 AJS Volume 129 Number 1 (July 2023): 123– 161 123