This is not an easy question to answer, because you have to count up all the properties for which we have tax assessor records and compare that to all the properties for sale in the MLS, on bank websites and on for-sale-by-owner websites.

Enter the great Arthur Patterson, a hyper-intelligent, near-mythical creature roaming the Redfin office in his socks at 7:15 a.m., oddly pleasant but always precise, and undoubtedly capable of assembling an atom bomb before breakfast.

Arthur helped put together the table below. He asked me to note that the percentages are probably a little too high, because our tax-records aggregator always misses a few properties but the margin of error is still less than 5%.

What immediately jumps out is how few homes are for sale compared to the number of properties available the city of San Francisco, where there are plenty of rental properties and the inventory of single-family homes is still slim.

At the other end of the spectrum, nearly 1 in 20 homes are for sale in Chicago, so there’s a lot of turnover in the heartland.

[And many thanks to Redfin reader Kim for  her comment on our photo of a Burmese python: "I suspected my x had once again fallen into the hands of the law."]