Why Has California’s Prison Population Fallen to Its Lowest Level in More Than 30 Years?

Susanto and Harris (2026) examined how California’s prison population has changed in recent years and what those changes reveal about incarceration patterns by race, gender, age, offense type, and prison spending. They analyzed California Department of Corrections and Rehabilitation (CDCR) prison population data and California state budget data from 2010 through 2025. They found that California’s prison population fell to about 90,600 inmates in 2025, a 27% decline since 2019. They also found major racial disparities, with Black Californians making up 6% of the adult population but 27% of imprisoned men. Young adults ages 18–24 experienced the largest imprisonment decline, falling 64% between 2019 and 2025.

Why This Article Was Selected for The Policy Scientist

This article addresses one of the most consequential long-term developments in American public policy: the large-scale decline in incarceration rates following decades of prison expansion. That topic has major implications for state budgets, labor markets, public safety, sentencing policy, racial disparities, and the long-term legitimacy of criminal justice institutions. The timing is especially important because California has now reached its lowest prison population in more than thirty years while simultaneously confronting debates over prison closures, correctional spending, and violent crime policy. Susanto and Harris contribute to a substantial California corrections literature by documenting how demographic composition, sentence length, and offense categories have evolved during this transition. The administrative CDCR data are strong descriptive data and likely highly reliable for population measurement. However, the study is primarily descriptive rather than causal.

Full Citation and Link to Article

Susanto, L., & Harris, H. (2026, April). California’s prison population. Public Policy Institute of California. https://www.ppic.org/publication/californias-prison-population/

Central Research Question

Susanto and Harris examine how California’s prison population has changed during the past several decades, with particular attention to the post-2019 period. Their central research question asks how the size, demographic composition, offense structure, sentencing patterns, and fiscal dimensions of California’s prison system have evolved as the state’s incarcerated population has declined to its lowest level in more than thirty years. The report also implicitly asks whether the prison population decline has been evenly distributed across racial, gender, and age groups, and whether prison downsizing has materially altered the operational and financial structure of the California Department of Corrections and Rehabilitation (CDCR).

The study is situated within a broader period of criminal justice transformation in California. Since the late 2000s, California has implemented several major policy reforms designed to reduce prison overcrowding and incarceration rates, including realignment policies, sentencing reforms, and pandemic-era population reductions. The report therefore attempts to provide an updated descriptive portrait of the California prison system after these overlapping institutional and demographic shifts.

The article also explores whether declining prison populations necessarily correspond to reduced correctional expenditures or meaningful structural changes within correctional institutions. By examining prison spending, sentence lengths, offense categories, and prison capacity utilization together, the authors frame incarceration as both a demographic and fiscal policy issue rather than solely a criminal justice issue.

Previous Literature

The report builds upon a substantial literature examining mass incarceration, prison overcrowding, sentencing policy, and racial disparities in imprisonment within the United States. California has occupied a central role in this literature because the state experienced one of the largest prison expansions in modern American history before later becoming a leading example of prison population reduction. Earlier research documented the rapid growth of California’s prison population beginning in the late 1970s, driven by mandatory sentencing laws, enhanced penalties, drug enforcement policies, and longer prison terms for violent offenses.

The literature also includes extensive analysis of California’s 2011 realignment reforms, which shifted responsibility for many lower-level offenders from state prisons to county systems following federal court intervention over unconstitutional prison overcrowding. Previous studies generally found that realignment substantially reduced prison populations without generating dramatic statewide increases in violent crime, although local impacts varied across jurisdictions.

Susanto and Harris contribute to this literature by updating descriptive trends through 2025, particularly after the disruptions associated with the COVID-19 pandemic. The report also extends prior work on racial disparities by documenting continuing disproportionality in imprisonment rates across demographic groups. Black Californians remain dramatically overrepresented within the prison population despite long-term declines in overall incarceration rates.

The article does not attempt to directly engage theoretical criminology debates or causal identification controversies in the literature. Instead, it functions primarily as an empirical status report summarizing the current structure of California incarceration. In that respect, it resembles institutional policy surveillance research rather than hypothesis-testing social science. Nevertheless, the report contributes useful updated descriptive evidence to ongoing debates surrounding decarceration, prison closures, sentencing reform, and correctional budgeting.

Data

The authors rely primarily on administrative data from the California Department of Corrections and Rehabilitation (CDCR), including Offender Data Points reports and prison population dashboards spanning 2019 through 2025. They supplement these incarceration records with California Department of Finance population estimates and California state budget data covering fiscal years from 2010 through 2025.

The dataset includes information on prison population counts, imprisonment rates, demographic characteristics, offense categories, sentence structures, prison design capacity, and correctional expenditures. The demographic analysis includes race, ethnicity, gender, and age distributions. Offense classifications include homicide, assault, sex crimes, robbery, burglary, and drug offenses. Fiscal data examine both total correctional spending and the share of the California General Fund allocated to corrections.

The administrative nature of the dataset represents one of the study’s primary strengths. Because the data originate directly from state correctional systems, they likely provide highly accurate measures of institutional populations and operational characteristics. The data are especially valuable for tracking longitudinal changes in incarceration rates and prison capacity utilization over time.

At the same time, the data have several limitations. The report notes that CDCR historically did not publicly disaggregate some racial categories, grouping several smaller populations into an “Other” category. This limits detailed subgroup analysis for Asian American, Native American, and other populations. Additionally, because the report relies almost entirely on aggregate administrative statistics, it cannot evaluate individual-level mechanisms driving incarceration trends or directly estimate policy effects.

The dataset is most useful for descriptive institutional analysis rather than causal inference. It provides a detailed overview of prison system characteristics but does not include the type of counterfactual comparisons typically required for stronger causal identification strategies.

Methods

The report employs descriptive statistical analysis rather than advanced econometric or causal inference techniques. The authors primarily use trend analysis, percentage comparisons, imprisonment rates per 100,000 residents, and cross-sectional demographic comparisons to describe changes in California’s prison population over time.

The methodology is straightforward and transparent. The authors compare incarceration levels before and after major institutional changes, especially the pandemic period and post-realignment era. They calculate percentage declines across demographic groups and identify differences in imprisonment rates by race, age, and gender. They also examine changes in offense composition, sentence structures, and prison capacity utilization.

Because the report is descriptive, it does not employ regression analysis, experimental methods, quasi-experimental designs, or formal hypothesis testing. The study therefore cannot isolate the independent causal effects of specific reforms such as realignment, sentencing changes, or pandemic-related release policies. Instead, the report documents correlations and temporal patterns.

This methodological approach is appropriate for a public policy fact sheet designed to summarize institutional trends for policymakers and the public. However, the analysis would be strengthened by future research using stronger causal inference methods. Difference-in-differences models, synthetic control approaches, or regression discontinuity designs could help identify the independent effects of specific policy interventions on incarceration rates, prison spending, and demographic disparities.

The absence of advanced statistical modeling also limits external validity and causal interpretation. The report successfully documents what changed within California’s prison system but provides less evidence regarding why those changes occurred or whether similar patterns would emerge under comparable policies in other states.

Findings/Size Effects

The report documents a dramatic long-term decline in California’s prison population. After increasing nearly eightfold between 1977 and 2006, California’s prison population fell to approximately 90,600 incarcerated individuals by December 2025. This represented a 27% decline relative to December 2019. California’s imprisonment rate also declined substantially, reaching 294 incarcerated adults per 100,000 residents in 2025.

The demographic findings reveal substantial disparities across racial, gender, and age groups. Men constituted 96% of the prison population in 2025, and the gender disparity in imprisonment rates widened during the pandemic period. The female prison population declined 34% between 2019 and 2025, compared to a 27% decline among men.

Racial disparities remained pronounced despite declining incarceration rates. Black Californians represented only 6% of the adult population but accounted for 27% of imprisoned men and 24% of imprisoned women. Latino Californians also remained overrepresented relative to their share of the state population. In contrast, white Californians were substantially underrepresented within prison populations relative to their population share.

The largest incarceration declines occurred among younger adults. Imprisonment rates for Californians ages 18–24 fell 64% between 2019 and 2025, declining to 99 incarcerated individuals per 100,000 residents. Adults ages 25–34 experienced a 30% decline. Individuals ages 35–44 continued to have the highest imprisonment rates despite recent reductions.

The offense composition of California prisons also shifted. By 2025, 52% of incarcerated individuals had been convicted of homicide or assault, up from 46% in 2019. Another 18% were incarcerated for sex crimes. Only 3% were imprisoned for drug offenses, reflecting the declining role of drug incarceration within California prisons.

Sentence severity remained substantial despite declining prison populations. More than one-third of incarcerated individuals were serving life or life-without-parole sentences, representing an 8 percentage point increase since before the pandemic.

The fiscal findings demonstrated partial but incomplete budgetary contraction. Correctional spending declined from $14.8 billion to $13.4 billion during the previous two years, and the CDCR share of the California General Fund fell from 8.6% to 5.9% between 2019 and 2025. However, annual incarceration costs per prisoner increased 9%, reaching approximately $127,800 per incarcerated person in 2026 dollars.

Conclusion

Susanto and Harris provide a comprehensive descriptive overview of California’s prison system during a period of major institutional transition. Their findings demonstrate that California has experienced substantial prison population declines while continuing to maintain large racial disparities, long prison sentences, and significant correctional expenditures.

One of the report’s most important contributions is its demonstration that prison downsizing does not necessarily eliminate structural inequalities within incarceration systems. Even as imprisonment rates declined sharply, Black Californians remained heavily overrepresented within the prison population, and violent offenders composed an increasing share of incarcerated individuals.

The report also illustrates the fiscal complexity of decarceration. Although total correctional spending declined, per-prisoner costs increased, suggesting that prison systems may not generate proportional cost savings as populations shrink. The persistence of high operational and health care expenditures further indicates that correctional institutions retain substantial fixed costs even after prison closures.

Methodologically, the study serves primarily as a descriptive institutional assessment rather than a causal evaluation of criminal justice reforms. Its administrative data are strong and likely highly reliable, but the absence of causal inference techniques limits conclusions regarding the independent effects of specific policy interventions. Future research using quasi-experimental designs could strengthen understanding of how sentencing reforms, prison closures, and demographic shifts interact to shape incarceration outcomes both within California and across other jurisdictions.