In 2017 Seattle added ~8700 new houses. Average household size in Seattle in 2 people. Figure it is probably under 2 on average for people moving to the city.

In 2017 Seattle added ~8700 new houses. Average household size in Seattle in 2 people. Figure it is probably under 2 on average for people moving to the city. So Seattle is under-building 2k-4k houses (conservatively! 10k worst case) per year, and has been for quite some time now. Of course prices are going up and people are being priced out.