Civic Data

Data-oriented thinking about where and how people live.

Visualizing population density: Bay Area


Population density is frequently described as people (or housing units) per acre. But I don’t have a good feel for how “people per acre” plays out in a real-life context. What does a street with 15 people per acre look like? One with 30 people per acre? A hundred per acre sounds like a lot — is it a lot?

With that in mind, I recently spent quite a bit of time combining a map of census block-level population data in QGIS with the awesome power of Google Street View to get a sense for what population density feels like at street level. I focused on the U.S. because the data was accessible to me, but I’d love to see similar explorations of living arrangements around the world — especially European and Japanese cities.

My strategy was to pick blocks across the metro area that represented a variety of population densities. This was done in a quasi-random way — I tried to distribute the locations around the metro area, and I haven’t picked particularly nice or ugly blocks. I just looked at a map of population densities, picked a likely block, navigated there in Street View, and snapped a screen shot. The population density numbers I quote are the averages of the two adjacent facing blocks.

A caveat is that I focused on streets that were primarily residential, which will have higher population densities than blocks which contain other uses mixed in. On the other hand, residential uses constitute a large majority of the acreage of any city (e.g. 48% for Berkeley), and the figures I quote do include the square footage of the surrounding streets, which constitute 15-25% of the area of a typical city (24% for Berkeley, from the same source).  On net, if you’re interested in bulk population density on a city scale — including shops, schools, offices, parks, etc — you’ll need to deflate these figures by something like 25%.

On to the pictures

1.8 people per acre (Danville):

1.8, Danville

At the low end, these densities are necessarily imprecise — lot and block sizes aren’t so clear from the air.

3.7 (Danville):

3.7, Danville

5.8 (Danville):

5.8, Danville

8 (Danville):

8, Danville

12 (Santa Cruz):

12, Santa Cruz

15 (Santa Cruz):

15, Santa Cruz

18.5 (Santa Cruz):

18.5, Santa Cruz
25 (Berkeley):

25, Berkeley

26 (Berkeley):

26, Berkeley

Both Berkeley and Santa Cruz have a reasonably high fraction of legal or illegal “granny flats” — a separate living unit at the back of the lot. You can see a few in this image.

40 (Santa Cruz):

40, Santa Cruz

50 (San Francisco):

50, San Francisco

Our first townhouse neighborhood is not so high-density: mostly two-story with fairly large backyards

65 (Berkeley):

65, Berkeley

Individual largish apartment buildings can contribute substantial density.

70 (San Francisco):

70, San Francisco

Three-story townhouses.

78 (San Francisco):

78, San Francisco

Slightly smaller lots.

85 (Berkeley):

85, Berkeley

Fairly large apartment buildings mix with single-family and duplex houses.

125 (San Francisco):

125, San Francisco

Mostly apartment buildings here.

135 (San Francisco):

135, San Francisco

Townhouses and apartment buildings. The Bay Area doesn’t get much denser than this.


2 thoughts on “Visualizing population density: Bay Area

  1. Pingback: Visualizing population density: Boston | Civic Data

  2. Pingback: Visualizing population density: New York City | Civic Data

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