The number is, as the San Francisco Chronicle described it, “startling.” Based on data from the San Francisco Police Department (SFPD), “burglaries” from vehicles were up 47% in the first six months of the year compared to 2014.

Law enforcement had been predicting a big jump in crime as two new policies take hold. Court-directed prison realignment assured that low-level felons spend less time in prison, to reduce severe overcrowding. And Proposition 47, passed in November, reclassified some felonies as misdemeanors.

The numbers improved in July, according to SF OpenData, the police department’s online crime database. But not enough to lower those raised eyebrows. OpenData shows a 46% increase in “larceny/theft” from locked and unlocked autos (petty and grand thefts) as of June 30, compared to the same period last year.

But that number drops to 42.8% on July 31 because during that extra month there were just 27.8% more crimes. There were 1,880 in 2014, compared to 2,384 this year. The online database draws information from an old police department reporting system, which is in the process of being retired over multiple years. But it is updated daily and the June 30 total for locked-vehicle incidents was within 260 of the 11,915 “burglaries” reported by the Chronicle. Eventually, the database will migrate to a new city portal, DataSF.

The database shows 15,822 total thefts from vehicles to date as of July 31, compared to 11,084 last year. The vast majority qualify as grand theft, 12,742 this year, while 3,080 are petty. Thirteen percent (2,099) of those submitting reports to the police indicated their cars were unlocked.

Not everyone files a police report, so it’s hard to interpret the statistics. But the 47% jump reported by the Chronicle resonated with some. S.F. Supervisor Scott Wiener, who represents the Castro, Noe Valley and parts of the Mission, said, “We’ve seen an absolute explosion of auto break-ins. There are areas in my district where you’ll have 10 cars on a single block that have been broken into.”

Everyday is apparently a good day to break into a car in San Francisco and steal something, but weekends are a little special. Saturday is the busiest day, with 2,133 reports of theft, followed by Friday, 2,093, and Sunday, 1,903. The other four days range between 1,817 and 1,839 incidents over the seven-month period.

Robert Weisberg, a professor of criminal law at Stanford Law School, told the Chronicle it’s dangerous to conjure up cause-and-effect scenarios based on a small sample of incidents, occurring in a short period time, with multiple variables involved. Deteriorating conditions for homeless people and declining police resources are among reasons cited for the spike.

“Nothing is harder to establish than causes of crime-rate changes—that’s especially true in the short run where there are so many volatile issues going on,” he said.

–Ken Broder

To Learn More:

Jump in S.F. Car Break-Ins Prompts Frustration, Finger-Pointing (by Evan Sernoffsky, San Francisco Chronicle)

Car Burglaries Spiking in San Francisco, Up 47 Percent Over Last Year (by Mark Matthews, NBC Bay Area)

SF OpenData (San Francisco Police Department)