This Twitter thread by UC Davis Law Professor, Chris Elmendorf, is a good reminder that there can be a meaningful difference between actual completed homes and zoned land that might one day becoming new housing.

The point he makes is as follows: The state of California's housing needs allocation for the city of San Francisco is approximately 80,000 new homes over the next decade. In the past, cities could demonstrate that they were able to meet these targets through, as I understand it, some fairly loose assumptions. But more recently, amendments have made it such that the probability of new homes actually getting built needs to be considered.

San Francisco has been doing this and, according to Chris, the conclusion was that the city should upzone portions of the city -- primarily on the west side -- to allow for some 22,000 new homes. Sounds cool. But as part of this process, the city also hired an outside consultant to run indicative pro formas and assess overall development feasibility. This is what they found:

I haven't seen any of the actual numbers, but what this chart is saying is that nobody is going to develop on the west side of the city no matter what entitlements you put in place (tier 3 and tier 4 market areas). The only new development that is likely to take place is high-rise development over 24 storeys in the highest value submarkets (tier 1 and tier 2 market areas).

Based on this, the 22,000 new homes figure is probably closer to 0 new homes.