The Building Permits Survey (BPS) is a survey of local governments on the number of new, privately-owned housing units they issued building permits for every year, issued by the US Census Bureau. (Some cities are surveyed every month, while some are surveyed annually.) The form they send out looks like this.
Not every housing unit that receives a permit is actually built. Some fraction of "housing permits" becomes a "housing start", and then some fraction of those become "housing completions".
The Census also does a survey on housing starts and completions as part of the Survey of Construction (SOC). They report that overall, for single-family housing, starts were 2.5% greater than permits, and completions were 3.5% less than starts. For multifamily, starts were 22.5% less than permits, and completions were 7.5% less than starts. I might try to add SOC data here at some point.
I'm not sure! They claim that only 5% of rows in the 2019 annual data survey had to be imputed because of nonresponse, but that doesn't mean that the officials in each city know how to fill out the form accurately. From other folks who've played with this data, I've gathered that the data is generally more reliable for bigger cities, whose bureaucracy is presumably more competent at filling out these forms, and less so for small towns.
The Census Bureau has their own tool for making tables from the BPS, so trying the same state/city and year there and comparing the two numbers might be a good start.
This is a work in progress! Feedback and feature ideas are welcome on GitHub.
Data from the US Census Building Permits Survey. Created by Sid Kapur.