San Francisco Burglary - Part 2, time-of-day patterns
Important! Read Part 1 first.
Burglary has been steadily increasing over the past twelve months in San Francisco. On average, citywide, it is up about 15%.
Geek Note: Most types of crime, including Robbery and Assault, are on a down trend in San Francisco. Burglary is not indicative of overall crime.
In the last post, we saw that burglary rates are uneven throughout San Francisco, being much higher in some areas than in others. We also saw that burglaries are decreasing in most parts of the city, but doubling in some neighborhoods!
We will show that burglaries have very strong time-of-day patterns in San Francisco. In some cases, adjascent neighborhoods show a 4x swing.
Search: Burglary rates citywide
First, lets look at burglary rates in San Francisco during 2018 by using Illuminated City Search.
Search delivers a 3-D visualization of a city, where the altitude/opacity of the "overcast" indicates the relative frequency of "searched" events. Just below is a search on all burglary crime types for 2018.
Burglary rates are clearly very different in different neighborhoods. In Part 1 we examined the areas where burglary increased and decreased over the past twelve months. Here we will look at something different.
Cycles: What are they?
When looking at a crime category, say drunk driving, we may discover that the incidents have a strong time-of-day pattern. Or a day-of-week pattern.
DUI is an obvious example but other crime categories also exhibit such patterns. To help see them, Illuminated City makes it easy to see them in both our 2-D charts and the 3-D geo-view. We call them Cycles
Geek Note: Chicago has month-of-year cycles — apparently February weather is not conducive for any activity, even criminal.
Examples of "cycles"
Lighting - time-of-day
Activities - day-of-week
Tourist season - month-of-year
Weather - month-of-year
Burglary Cycles in San Francisco
Let's look at San Francisco burglary by charting two cycles, Day and Night. Day goes from 6:30am to 6:30pm; night is from 6:30pm to 6:30am.
Conveniently, San Francisco burglaries for the past twelve months are split evenly between Day and Night. But that is a citywide average. Perhaps we will see interesting patterns within a neighborhood.
Burglaries by time-of-day
One would expect neighborhood burglaries to reflect the city ratio, 50:50. Instead, we see surprisingly strong patterns by neighborhood.
Geek Note: Reminder, the overall distribution of burglaries is exactly even between night and day.
Target: Specific details
Those colors are nice, yeah? But one might ask, how strong is the bias? We did.
Using the Target feature, we took a look at couple of neighborhoods. Some neighborhoods had a strong "bias" for burglaries at night; others had a strong bias for daytime burglaries. Something is driving this — we don't know what.
The chart below shows a summary of four Target selections aiming to show information for the areas with the greatest rise in burglaries.
Actionable specifics: A pattern of behavior
To select one specific neighborhood: Refer to the area combining C and D above. Despite being directly adjascent, C and D show opposite time-of-day behavior.
During the day, burglaries are twice as likely to occur in Area C (than D).
At night burglaries are twice as likely to happen in Area D (than C).
Geek Note: This pattern has been set by 100 burglaries over a twelve month period — it is not a statistical anomaly.
There are a dozen other areas in San Francisco with such strong night/day patterns for burglary.
Next post: Some other fascinating geo-patterns
Using the Search and Compare features sometimes shows some interesting – and mystifying – patterns.
We will leave the beautiful city of San Francisco for our next post.