Research Summary: Our study represents the first effort to evaluate systematically Proposition 47's (Prop 47's) impact on California's crime rates. With a state-level panel containing violent and property offenses from 1970 through 2015, we employ a synthetic control group design to approximate California's crime rates had Prop 47 not been enacted. Our findings suggest that Prop 47 had no effect on homicide, rape, aggravated assault, robbery, or burglary. Larceny and motor vehicle thefts, however, seem to have increased moderately after Prop 47, but these results were both sensitive to alternative specifications of our synthetic control group and small enough that placebo testing cannot rule out spuriousness. Policy Implications: As the United States engages in renewed debates regarding the scale and cost of its incarcerated population, California stands at the forefront of criminal justice reform. Although California reduced its prison population by 13,000 through Prop 47, critics argue anecdotally that the measure is responsible for recent crime upticks across the state. We find little empirical support for these claims. Thus, our findings suggest that California can downsize its prisons and jails without compromising public safety.

California has fundamentally reformed its criminal justice system. Since 2011, the state passed several reforms which reduced its massive prison population. Importantly, this decarceration has not harmed public safety as research finds these measures had no impact on violent crime and only marginal impacts on property crime statewide. The COVID-19 pandemic furthered the state’s trend in decarceration, as California reduced prison and jail populations to slow the spread of the virus. In fact, in terms of month-to-month proportionate changes in the state correctional population, California’s efforts to reduce overcrowding as a means to limit the spread of COVID-19 reduced the correctional population more severely and abruptly than any of the state’s decarceration reforms. Although research suggests the criminal justice reforms did not threaten public safety, there is reason to suspect COVID-mitigation releases did. How are COVID-19 jail downsizing measures and crime trends related in California, if at all? We address this question in the current study. We employ a synthetic control group design to estimate the impact of jail decarceration intended to mitigate COVID-19 spread on crime in California’s 58 counties. Adapting the traditional method to account for the “fuzzy-ness” of the intervention, we utilize natural variation among counties to isolate decarceration’s impact on crime from various other shocks affecting California as a whole. Findings do not suggest a consistent relationship between COVID-19 jail decarceration and violent or property crime at the county level.

In the current study we use a synthetic control group design to estimate the causal effect of a medical marijuana initiative on suicide risk. In 1996, California legalized marijuana use for medical purposes. Implementation was abrupt and uniform, presenting a "natural experiment." Utilizing a panel dataset containing annual frequencies of Total, gun, and non-gun suicides aggregated by state for the years 1970-2004, we construct a control time series for California as a weighted combination of the 41 states that did not legalize marijuana during the analysis period. Post-intervention differences for California and its constructed control time series can be interpreted as the effects of the medical marijuana law on suicide. Significance of the effects were assessed with permutation tests. Our findings suggest that California's 1996 legalization resulted in statistically significant (p<.05) reductions in suicides and gun suicides, but only a non-significant reduction in non-gun suicides (p≥.488). Since the effect for non-gun suicides was indistinguishable from chance, we infer that the overall causal effect was realized through gun suicides. The mechanism could not be determined, however. Participation in the medical marijuana program legally disqualifies participants from purchasing guns. But since most suicides involve guns, it is possible that the effect on total suicide is driven by gun suicide alone.