TRERC, and Zillow: Why don’t the numbers add up?

Bryan Pope
From time to time, clever users of our housing data have asked us why our data is not synchronized – sometimes significantly – with the numbers provided by other major data sources. One such question came to us this week:

"I wonder why your data only shows 43,507 listings from Texas, while Zillow and have 79,344 and 146,265 for Texas. I realize that some listings remain on this site for several weeks after they were sold for marketing reasons, but it’s still a significant difference. And most listings come from MLS, or so I was told."
Gerald Klassen, a data researcher here at the Texas Real Estate Research Center, has shed some light on the subject.
"Our number of 43,507 is the number of active status statements open on the last day of the month," he said. "We only count offers of family houses, flats and town houses. We use this data to calculate a monthly stock, which tells you how long it would take for the market to relax if no new offers came to market."
Zillow and, meanwhile, provide a number of listings from the moment a person searches their website. By the end of the month, many homes will be sold and several will be withdrawn from the market. New offers are added continuously, usually at the beginning of the month.
"I just filtered by type of real estate on and currently there are 98,599 offers of family houses, apartments and town houses in Texas," said Klassen. "If you hide pending / conditional statements, this number drops to 39,452 in the active state. This is not far from what we display as active listings on our site. On this number, it’s amazing that more than half of the offers on are pending or conditional. What we have seen in this pandemic housing boom is that the average time to market has shortened, while the average time to foreclosure has lengthened. People find it difficult to get the services needed to close a home sale / purchase."
The difference between the number of active records of the Center and the number of Zillow or can be caused by the search time, the type of record property and the status of the record.
"It’s amazing to think we can have record home sales and so few active ads," said Klassen. "Out-of-market listings in many areas fell by 50 to 70 percent compared to last year. This means that almost everything that comes to market goes through sales."
David Berry

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