California says crime is down. But officials know the data is flawed

San Francisco Chronicle​

5 days ago

It happened again.
The California Department of Justice this week published a major report, and a corresponding press release, touting a drop in violent crime across the state. But the data underlying the report is substantially flawed — thanks to a big mistake that the DOJ was made aware of last year after Chronicle reporting, but did not fix.
In last year's Crime in California report, the Chronicle found that Oakland had logged an improbably high violent crime spike in 2023, fueled by a reported 138% jump in aggravated assaults — a number that did not match Oakland's own year-end report.
After the Chronicle inquired, Oakland police said the anomaly was due to 'human error.' When the newspaper brought the problem to the head of the DOJ, Attorney General Rob Bonta, a spokesperson pinned the blame on Oakland. The office did not issue any correction to the statewide numbers in the report.
This year, the state again used the faulty numbers in its report, despite knowing they were incorrect. The office did not respond to questions about why it did not correct the known error in the data. In the report, it pointed users to Oakland's website, saying to 'use caution' in comparing 2023 numbers to any other year.
But the state did not heed that advice in its own press release, citing a 6% decrease in violent crime in the state between 2023 and 2024. Had the state corrected the 2023 numbers using the Oakland police data that it linked to, violent crime statewide would have decreased by 2%, according to a Chronicle analysis.
The error distracts from what are otherwise promising long-term trends in California crime rates. Even after correcting for the flaw, levels of both reported violent and property crime are well below the historic highs of the 1980s and 90s, and continued to trend downwards in 2024. Homicides across the state have come back down from pandemic-era surges and have continued to decline this year, according to the Real-Time Crime Index, which compiles data from local agencies. San Francisco reported a 60-year low in killings last year.
Asked last year whether the state checks to ensure the accuracy of data in its reports, the attorney general's office said staff members ask local police departments about anomalous data if they notice it, but that they do not have the responsibility to do so.
'The onus is on every police department to report accurate data. Our role is to publish a comprehensive report based on what each of the 500+ agencies are responsible for reporting to us,' a spokesperson said in an email last year. 'Any discrepancy is the responsibility of the local agency.'
But on the fourth page of the report, the DOJ notes that the role of the Criminal Justice Statistics Center, which compiles the report, is to 'collect, analyze, and report statistical data that provide valid measures of crime, to 'examine these data on an ongoing basis to better describe crime' and to 'promote the responsible presentation and use of crime statistics.'
Researchers and advocates rely on the state's crime data reports to analyze trends, measure the impact of policy changes and make criminal justice recommendations. In the press release that came alongside the reports, Bonta's office pointed to them as 'vital' information that can be used to 'support informed policy choices.'
Magnus Lofstrom, the criminal justice policy director at the Public Policy Institute of California, said that the flawed report 'is of concern.' But he noted that the DOJ provided several caveats with the data, which included this year's note cautioning people against using 2023 as a comparison.
Lofstrom said that, in addition to the Oakland mistake, the number of agencies that reported incomplete data was 'unusually high' in 2023.
What that means is that, for every report based on the state data, Lofstrom and his team must manually correct several of the numbers on the individual agency level in its analyses, substituting in estimates based on the averages and shares of crimes in other months.