December 10, 2021
It’s been 25 years since Californians voted to allow medical cannabis use. In 2011, the state further loosened cannabis restrictions by decriminalizing the drug and reducing the penalties for marijuana crimes, including reducing many offenses from misdemeanors to infractions. Five years ago, voters passed a proposition that legalized the use, sale and cultivation of recreational cannabis.
This data-driven project asks the question: how have marijuana arrests in California changed throughout this time period?
The arrest data in this project was sourced from the California Department of Justice. It draws from an annual report the department publishes called Crime in California. The original reports are published on the department’s website here. The population data used in this analysis was published by the US Census Bureau. That data can be found here and here.
First let’s look at changes in the number of marijuana arrests in the state over time.
Before decriminalization in 2011, misdemeanor arrests made up a significant majority of cannabis arrests in California. As we can see, misdemeanor arrest numbers dropped dramatically in 2011, which significantly reduced the total number of marijuana arrests in the state.
Interestingly, there were more felony marijuana arrests per person in California than misdemeanor arrests from 2011 through 2015. It wasn’t until 2016, when the state legalized recreational marijuana, that felony arrests dipped back below misdemeanors.
This graphic shows the total number of annual drug arrests in California. The green portion of each bar graph represents marijuana arrests and the orange section represents the combined number of arrests for all other drug crimes.
2020 saw the fewest number of statewide drug arrests in two decades. It was also the year with the lowest number of marijuana arrests.
Finally, let’s look at the age demographics of who has been arrested for marijuana crimes over time.
This heatmap shows that people 29 and younger are disproportionately arrested for marijuana crimes compared to older people. That is especially true for people who are 20 to 29 years old. That age group has consistently been more than twice as likely to be arrested than would be predicted by their makeup in the total population. What exactly is causing that disproportionate arrest rate, whether it’s rooted in law enforcement practices or the rate at which people in the various age groups commit marijuana crimes, is a reporting question that extends beyond what this data can tell us.
However, it’s interesting to note that 2011 marked a shift in the age demographics of arrestees. It’s possible that the decriminalization of marijuana is connected to that change, although more reporting would be required to say that definitively. Beginning in that year, it appears that the share of arrestees aged 20 to 29 went down, although people in that age group were still arrested disproportionately. We can also see that in 2012, the 30 to 39 year old age group moved into a positive percentage, meaning that they were, for the first time, disproportionately more likely to be arrested for a marijuana crime compared to their portion of the population.
This project was created for the fall 2021 Data Visualization course at the UC Berkeley Graduate School of Journalism, taught by Professor Peter Aldhous. You can learn more about this project and the data analysis behind this graphics at this Github repository.