County-level decarceration atlas: mechanisms, prevalence, and dynamics of decarceration across 2,870 U.S. counties, 1999-2019

Decarceration, the process of reducing incarceration rates, is increasingly viewed as a strategy to improve population health and reduce health inequities. Yet, evidence on its health effects remains limited and may depend on how decarceration occurs. We developed a national decarceration "atlas" to characterize the mechanisms and dynamics of decarceration across more than 2,800 U.S. counties between 1999-2019. Using longitudinal county-level jail and prison data, we identified four operational types of decarceration: reduced pretrial detention, reduced jail time, reduced prison admissions, and reduced prison time. Nearly two-thirds of counties, including most rural counties, experienced at least one decarceration type during the study period. Declines typically followed periods of recent growth and were relatively modest in magnitude, with median reductions of 19% to 38% ten years after onset. The frequency and timing of decarceration types varied by urbanicity, state, and region, with many counties experiencing multiple mechanisms concurrently. Validation against documented case studies of state and local decarceration demonstrated alignment with known legislative and de facto drivers, while revealing substantial sub-state heterogeneity. This atlas provides a scalable framework and hypothesis-generating resource to support comparative studies of decarceration's heterogeneous health effects.