# Visible Homelessness in SF: A Quick Breakdown of Causes

Anyone who's visited downtown San Francisco has seen streets like this one:

![](https://39669.cdn.cke-cs.com/rQvD3VnunXZu34m86e5f/images/6a1b04e4f186ea28416539c89116d65527cc419ee38f72ec.webp)

The US is the [richest country on Earth](https://en.wikipedia.org/wiki/List_of_countries_by_GDP_(nominal)_per_capita), excluding small states like Singapore with <10 million people. And the Bay Area is one of the US's economic hubs. Why do we see stuff like this? I'll try to break it down quickly. 

First, San Francisco is obviously an expensive place to live. Do housing costs predict high homelessness?

![](https://39669.cdn.cke-cs.com/rQvD3VnunXZu34m86e5f/images/949a0bdcffed34395b1dfd6a2d64c87ded76de185fd8f0a1.png)

They do! R^2 = 0.69 is really good. (This is a regression on US states, data from [here](https://meric.mo.gov/data/cost-living-data-series) and [here](https://endhomelessness.org/homelessness-in-america/homelessness-statistics/state-of-homelessness-2021/). Washington, DC is a high outlier; removing it raises R^2 to 0.73. High outliers include DC, Washington, Nevada, Alaska and New Mexico; low outliers include Maryland, New Jersey, Connecticut, Rhode Island and Virginia, although the first might be an artifact of DC being outside state borders.)

SF's housing costs are [3.3x higher](https://www.numbeo.com/cost-of-living/region_rankings_current.jsp?region=019) than the US average. Plotting it on this line, we should expect a homelessness rate of 0.7%, 5.8x higher than a city with normal rents. The actual rate is [0.9%](https://hsh.sfgov.org/wp-content/uploads/2020/01/2019HIRDReport_SanFrancisco_FinalDraft-1.pdf), another 1.3x higher than we'd expect compared to rent.

However, there are two other big factors to consider. #1 is that San Francisco has a very strong concentration of homeless people downtown. Here's a [breakdown by supervisor district](https://hsh.sfgov.org/wp-content/uploads/2020/01/2019HIRDReport_SanFrancisco_FinalDraft-1.pdf):

![](https://39669.cdn.cke-cs.com/rQvD3VnunXZu34m86e5f/images/c254c0df83bec14a61f6f0877395bb4c44922e05e813110c.png)

Districts are drawn to have equal populations, so District Six, which includes a lot of downtown buildings and office space, has a 5.1x higher rate of homelessness even compared to SF's average. Most cities don't have that. Eg. New York City has roughly the same homelessness rate as SF, but homelessness is more [evenly spread through the city](https://citylimits.org/2019/09/10/data-drop-which-nyc-neighborhoods-host-the-most-homeless-shelter-beds/); and the worst 10% of neighborhoods are split between the Bronx, Brooklyn, and Queens, instead of being concentrated downtown. 

Factor #2 is homeless people who are sheltered vs. unsheltered. Unsheltered homeless people sleep outside or in vehicles, so they're much more visible. [68%](https://hsh.sfgov.org/wp-content/uploads/2020/01/2019HIRDReport_SanFrancisco_FinalDraft-1.pdf) of San Francisco homeless are unsheltered, compared to [25%](https://www.huduser.gov/portal/datasets/ahar/2019-ahar-part-1-pit-estimates-of-homelessness-in-the-us.html) for the US outside of California. That's another factor of 2.7x.

Summing it up, we have:

| **Cause of visible homelessness** | **Factor of** | **Percent of all causes** |
| --- | --- | --- |
| SF has higher housing costs | 5.8x | 38% |
| SF has more homeless, adjusting for rents | 1.3x | 6%  |
| Homelessness concentrated downtown | 5.1x | 35% |
| SF homeless are more unsheltered | 2.7x | 21% |
| **Total** | **103.8x** | 100% |

(Note that, since these causes are multiplicative, percentage here is calculated by first taking the log, then dividing.) So, in total, visible homelessness is two orders of magnitude higher in SF than the US average, even though SF as a whole only has 30% more than you'd expect compared to rents.

Many assume that cold weather is a factor in homelessness, but I didn't find any relationship there:

![](https://39669.cdn.cke-cs.com/rQvD3VnunXZu34m86e5f/images/e7cd9a7041fb2c0d595eb3f1fd25da8af5b1d1defccbe798.png)

(weather data from [here](https://www.currentresults.com/Weather/US/average-state-temperatures-in-winter.php))

although it probably plays a role in whether homeless people are sheltered or not:

![](https://39669.cdn.cke-cs.com/rQvD3VnunXZu34m86e5f/images/0ac54bf63e0d8ac0a305b54414ea23b076ad158721d151c0.png)

so including San Francisco's mild winters as a factor in unsheltered homelessness, we get this table:

| **Cause of visible homelessness** | **Factor of** | **Percent of all causes** |
| --- | --- | --- |
| SF has higher housing costs | 5.8x | 38% |
| SF has more homeless, adjusting for rents | 1.3x | 6%  |
| Homelessness concentrated downtown | 5.1x | 35% |
| SF homeless are more unsheltered (weather) | 1.6x | 10% |
| SF homeless are more unsheltered (other) | 1.7x | 11% |
| **Total** | **103.8x** | 100% |

I also found that, controlling for rents, the partisanship of a state did not predict homelessness (using the [Partisan Voting Index](https://en.wikipedia.org/wiki/Cook_Partisan_Voting_Index)):

![](https://39669.cdn.cke-cs.com/rQvD3VnunXZu34m86e5f/images/c882f145167985fb095ec03590e617c7cebab5d6939c4e60.png)

Lastly, many people mix together homelessness and crime - assaults, harassment, car break-ins and so on, although many homeless people are not criminals and vice-versa. San Francisco has a dramatically higher rate of property crime than any other county in California, combined with fewer arrests than most places:

![](https://39669.cdn.cke-cs.com/rQvD3VnunXZu34m86e5f/images/f9be602721b29aefce6eb7b0d09efe3842c02fdb3b85b94d.png)

The trend with violent crime is a bit less extreme, but still there:

![](https://39669.cdn.cke-cs.com/rQvD3VnunXZu34m86e5f/images/8da770080f3396179685e40a5c75cf9cc41f108d9e355c18.png)

(Data from [here](https://www.ppic.org/wp-content/uploads/key-factors-in-arrest-trends-and-differences-in-californias-counties.pdf); note that this data is from 2014-16 and predates many recent controversies.) High homelessness, high crime, and a low arrest rate probably combine to create an overall, ambient feeling of danger in SF, more than any one factor by itself.