5 ms·

it's clearly not a covid effect https://www.sfchronicle.com/projects/sf-car-breakins/ https://www.sfchronicle.com/projects/sf-car-breakins/

ceejayoz 7mo ago
The spike in your link's chart clearly starts in early 2020. And "While our data extends only to 2018" is... important, yeah?
- whimsicalism 7mo ago
  i encourage other people reading to look at the chart so they can assess the veracity of ^ comment
  - ceejayoz 7mo ago
    Here it is. https://imgur.com/a/FK3sfna https://imgur.com/a/FK3sfna There's an enormous drop in edit: late 2019, and the second drop starts in 2023. https://www.sanfranciscopolice.org/your-sfpd/policies/department-bulletins-notices/24-052 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.
    - whimsicalism 7mo ago
      that drop is obviously in early 2020, not 2019 and there is no way you can look at that chart and describe car breaks ins as a "COVID blip"
      - ceejayoz 7mo ago
        Look at the X axis labels again. 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 https://imgur.com/a/i00Gna0 "that drop is obviously in early 2020", to reemphasize, is several years before the cameras got installed.
- conductr 7mo ago
  I read this as 2020 was Covid related drop, it then returned to normal for 2 years, then began dropping again in late 2023. The covid blip is explained by what was going on at the time, nothing since 2023 has any explanation and could be flock
  - ceejayoz 7mo ago
    COVID makes it spike up (after a months long downward trend long before the cameras), not down. Nation-wide, incidentally. The cameras were added where the black rectangle is here: https://imgur.com/a/i00Gna0 https://imgur.com/a/i00Gna0
    - conductr 7mo ago
      There are two nearly identical peaks on this chart. The trough between them is Covid. I’m not seeing anything I can call a Covid spike
      - whimsicalism 7mo ago
        well that's because you're discussing in good faith
        ceejayoz 7mo ago
        Where am I using bad faith?
      - ceejayoz 7mo ago
        The lowest point of the first trough is when COVID starts. It then rapidly increases and stays high for two years.
        conductr 7mo ago
        It looks like that rapid increase was a return to pre-covid normal. It never spikes above pre-covid. Given the world was returning to normal, this is precisely what you'd expect most trends to look like, something like in-restaurant dining probably looks similar.
arjie 7mo ago
The data is open, and so we don't have to do the visual reasoning off an imperfect graph. SF Chronicle has done a pretty rare (but I think good journalistic practice) of specifying the source of the data: https://data.sfgov.org/Public-Safety/Police-Department-Incident-Reports-2018-to-Present/wg3w-h783/about_data https://data.sfgov.org/Public-Safety/Police-Department-Incid... 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_Break-Ins_Reports_Heatmap_2018_to_Mar_2026_Incomplete.png 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_Changepoint_2018_to_Mar_2026_Incomplete.png 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.
- whimsicalism 7mo ago
  Your analysis also supports a covid trough, not a covid peak and certainly no covid effect. I agree with other commentators suggesting that flock cameras are not the full or even most of the story, but absolutely disagree with the GP that car break-ins are some identifiable covid phenom or that the decrease is merely a post-covid return to normalcy. Hopefully there was nothing wrong with posting a news article with a graph instead of doing the data analysis myself.
johnvanommen 7mo ago
That is a heck of a graph

ceejayoz 7mo ago

The spike in your link's chart clearly starts in early 2020. And "While our data extends only to 2018" is... important, yeah?

whimsicalism 7mo ago
i encourage other people reading to look at the chart so they can assess the veracity of ^ comment
- ceejayoz 7mo ago
  Here it is. https://imgur.com/a/FK3sfna https://imgur.com/a/FK3sfna There's an enormous drop in edit: late 2019, and the second drop starts in 2023. https://www.sanfranciscopolice.org/your-sfpd/policies/department-bulletins-notices/24-052 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.
  - whimsicalism 7mo ago
    that drop is obviously in early 2020, not 2019 and there is no way you can look at that chart and describe car breaks ins as a "COVID blip"
    - ceejayoz 7mo ago
      Look at the X axis labels again. 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 https://imgur.com/a/i00Gna0 "that drop is obviously in early 2020", to reemphasize, is several years before the cameras got installed.
conductr 7mo ago
I read this as 2020 was Covid related drop, it then returned to normal for 2 years, then began dropping again in late 2023. The covid blip is explained by what was going on at the time, nothing since 2023 has any explanation and could be flock
- ceejayoz 7mo ago
  COVID makes it spike up (after a months long downward trend long before the cameras), not down. Nation-wide, incidentally. The cameras were added where the black rectangle is here: https://imgur.com/a/i00Gna0 https://imgur.com/a/i00Gna0
  - conductr 7mo ago
    There are two nearly identical peaks on this chart. The trough between them is Covid. I’m not seeing anything I can call a Covid spike
    - whimsicalism 7mo ago
      well that's because you're discussing in good faith
      - ceejayoz 7mo ago
        Where am I using bad faith?
    - ceejayoz 7mo ago
      The lowest point of the first trough is when COVID starts. It then rapidly increases and stays high for two years.
      - conductr 7mo ago
        It looks like that rapid increase was a return to pre-covid normal. It never spikes above pre-covid. Given the world was returning to normal, this is precisely what you'd expect most trends to look like, something like in-restaurant dining probably looks similar.

arjie 7mo ago

The data is open, and so we don't have to do the visual reasoning off an imperfect graph. SF Chronicle has done a pretty rare (but I think good journalistic practice) of specifying the source of the data: https://data.sfgov.org/Public-Safety/Police-Department-Incident-Reports-2018-to-Present/wg3w-h783/about_data https://data.sfgov.org/Public-Safety/Police-Department-Incid... 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_Break-Ins_Reports_Heatmap_2018_to_Mar_2026_Incomplete.png 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_Changepoint_2018_to_Mar_2026_Incomplete.png 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.

whimsicalism 7mo ago
Your analysis also supports a covid trough, not a covid peak and certainly no covid effect. I agree with other commentators suggesting that flock cameras are not the full or even most of the story, but absolutely disagree with the GP that car break-ins are some identifiable covid phenom or that the decrease is merely a post-covid return to normalcy. Hopefully there was nothing wrong with posting a news article with a graph instead of doing the data analysis myself.

johnvanommen 7mo ago

That is a heck of a graph