First to match the graph you make sure you pick 'Larceny - From Vehicle' only (there are some others one might argue matter) and ensure you're only counting incidents once (many rows reference the same incident). That lets us recreate the original graph.
When looking at many things I like to look at seasonal effects just to see, and it doesn't look like they are significant here (but you can see the Mar 2020 drop to the next year quite easily which I like): https://wiki.roshangeorge.dev/w/images/2/2e/SFPD_Vehicle_Bre...
I also tried overlaying various line charts but that's useless for visually identifying the break.
One thing I thought would be fun is to run a changepoint algorithm blindly https://wiki.roshangeorge.dev/w/File:SFPD_Vehicle_Break-Ins_...
I like PELT because it appeals to my sensibilities (you don't say ahead of time how many changepoints you want to find - you set an energy/cost param and let it roll) and it finds that one changepoint. You can have some fun with the other algos and changing the amount of breakpoints or changing the PELT cost function. And then you can have even more fun by excluding 2020 or excluding Mar 2020 onwards or replacing it by estimates from the previous years (quite suspect considering what we're trying to do but hey we're having fun - a bunch of algos all flag Nov 2023 as some moment of truth)
Anyway, anyone curious should download the data. It's pretty straightforward to use and if I goofed up with off-by-one or whatever, you can go see for yourself.
And "While our data extends only to 2018" is... important, yeah?
There's an enormous drop in edit: late 2019, and the second drop starts in 2023.
https://www.sanfranciscopolice.org/your-sfpd/policies/depart...
> Starting on March 19, 2024, Flock Safety began installing ALPR cameras in various strategic locations across San Francisco. This rollout is expected to take place over the next 90 days. Per 19B ALPR policy, the administration of the Flock ALPR system is the responsibility of the Investigations Bureau.
How did the Flock cameras cause two crime drops before their installation?
The article's note about 2018 is talking about extending backwards, not forwards. It's entirely accurate, and a direct quote from your link.
The chart is trending down by January 2020, changes directions (upwards) right around the March 2020 spot, and again around (down) the July 2023 spot.
The fact that they only have data going back to 2018 means it's hard to say if the pre-COVID stuff was the norm or unusual.
To be super-clear, here's the chart annotated to show that 90 day window (black rectangle) in which the cameras were installed. https://imgur.com/a/i00Gna0
"that drop is obviously in early 2020", to reemphasize, is several years before the cameras got installed.
The cameras were added where the black rectangle is here: https://imgur.com/a/i00Gna0