Quick look at the 2022-23 data

One of the simplest things we can do is to simply count up all the police stops in all of the Los Altos data, and count them by race. Here's what you get when you do that with the Los Altos RIPA data:

	Total Stops	Stops per hundred per year	Relative per capita rate	Transient population required to equalize stops
White	1843	6.9	1.00	17735
Hispanic/Latino/a	1137	55.9	8.06	10941
Asian	798	7.6	1.10	7679
Middle Eastern or South Asian	587	14.9	2.15	5649
Black/African American	191	87.8	12.68	1838

"Total Stops" is easy, that's just all the stops the police made. Unsurprisingly, most of the people stopped by the police in Los Altos are white -- because most of the people in Los Altos are white.

Suppose we try to normalize that by the population of each race in Los Altos. It's not as easy as it might seem to get those numbers, because not everyone has the same divisions of race. I used a combination fo the 2020 US Census data and the World Population Review. So now we can divide the number of stops by the appropriate population. We'll also annualize it to make it easier to think about.

Now the "Stops per hundred per year" tells you how many people out of a hundred are likely to get stopped in any given year. You can also read this as the chance that you will get stopped -- if you are Asian in Los Altos, you have a 7.6% chance of getting stopped by the police each year.

We can immediately see there are some stark differences in how often people get stopped. For most people of color, this isn't surprising at all -- they have personally been stopped pretty often. In Los Altos, this says that for every 100 Black people in Los Altos, there are 87.8 stops. Of course, this probably means that some people are being stopped more than once. 

To put that in context, let's adjust the numbers to make the per-capita per-year stop rate for whites be our baseline. The "Relative per-capita rate" column shows us that Black people are 12.68 times more likely to be stopped than whites. Now, there will always be some statistical variation around that number, but even if it's only 10 times (or as many as 14 times!) that is still a big effect. Latinos are 8 times more likely to be stopped.

Now here's where a nuance of Los Altos comes in. This town is has some extremely expensive real estate, and was historically redlined. So many of the people of color who work or play in Los Altos are not counted as part of the population. Maybe that disparity is caused by the Black and Latinos who come to Los Altos each day.

After all, the next highest population group in Los Altos is Asian, and the Asian stop rate is very nearly the same as the white stop rate.

Well, we can test that. We simply ask, "How many Black or Hispanic people would have to come into Los Altos each day, such that if the police were making unbiased stops, we would see these stop rates?" Imagine an example: if the Hispanic population were 8 times what it is, then when we normalize the Hispanic stops to that new temporary population, we'd get the same stop rate that we get for whites. So, we simply multiply the "Relative per-capita rate" to get the last column, "Transient population required to equalize stops."

That last column tells us the number of people that would have to be coming in to Los Altos each day to explain the variation in stop rates. Do the numbers seem plausible to you? They don't to me. 1,838 Black folks would need about 900 cars, I would guess. Our parking problems would be a lot worse. And over 10,000 Latino folks would represent about a third of our whole population. We certainly have a lot of Latino folks coming into Los Altos to work, but there cannot be that many.

So if transient folks passing through Los Altos can't be the reason for the disparity, it seems like the experience of Los Altos people of color is borne out by the data: they are more likely to be stopped.