The fight between Compass, the country’s largest brokerage, and Zillow, its largest listing portal, has been covered as a corporate turf war — dueling lawsuits, a judge in Chicago ordering tens of thousands of listings restored, executives trading accusations. A two-day federal hearing wrapped in Chicago on July 2, with post-hearing briefs due July 9 and a ruling to follow. That framing is comfortable, and it misses what is actually at stake: the integrity of the data the mortgage system uses to price homes and the loans against them.
Here is the part the turf-war coverage skips
When a home is appraised, the value isn’t conjured; it’s triangulated from recent comparable sales, drawn overwhelmingly from the Multiple Listing Service — the shared database brokers maintain that feeds the public search sites. Lenders underwrite against that appraisal.
Government-backed entities buy and securitize the mortgages. The automated valuation models behind Zillow’s “Zestimate” and the banks’ own risk systems train on the same transactions. The entire collateral chain assumes one thing — that the record of what sold, when and for how much is reasonably complete and honest.
Compass wants to change that record’s completeness. The firm’s strategy is to market homes privately first — to its own agents and clients, then on its own website — and release them to the shared database only later, if ever. Market a home privately for weeks, test and cut the price out of public view, then enter it into the record scrubbed of that history, and you haven’t merely hidden a listing.
A home first offered at $900,000, cut twice, and sold at $825,000 tells a very different story than the same house appearing only as a clean $825,000 sale. The first signals softening demand; the second erases it. Appraise the next house on the block off that clean number, and you’ll set it too high — and so will every model that learns from it.
Days on market is the housing market’s odometer
There is a plainer name for this. Days on market is the number a buyer reads to judge how hard a listing has been driven and how motivated the seller has become — and the private phase quietly winds it back to zero. Congress made turning back a car’s odometer a federal crime in 1972 because the mileage is a material fact buyers rely on. The housing version carries no such penalty. It carries a friendlier name.
Why push the market this way? Follow the economics. Compass has never posted a full year of profit since its 2021 IPO. In a thin-margin business, the asset worth controlling is inventory and the data around it. And the firm’s own internal materials, cited in Zillow’s antitrust complaint, indicate its private listings end with Compass representing both buyer and seller — keeping the full commission rather than splitting it — about 72% more often than listings taken straight to the open market (roughly 31% of off-market sales versus 18%).
For the record, Compass says it doesn’t encourage double-ending. None of this is illegal. It is simply a structural reason a brokerage might prefer the private path, whatever the net to the seller.
And this is not an outsider’s theory. The MLS now at the center of the Chicago case — Midwest Real Estate Data — warned of exactly these harms in its own 2019 white paper, cautioning that homes held off the MLS leave “incomplete historical records that limit appraisals, CMAs and county assessor valuations,” before it partnered with Compass to take the private model national. The firm now selling the private path once documented the damage it does to the record you price against.
This was never really about one seller’s choice
A homeowner who markets privately may do fine, and privacy is a legitimate aim — a celebrity, a judge, a domestic-violence survivor may reasonably want it. The question is not whether private listings should exist; it is what happens to price discovery when they stop being the exception and become a mainstream strategy.
One home off the books is a choice. A meaningful share of the market off the books degrades the shared record for everyone — including the buyers, appraisers, lenders and investors who never opted in.
This is where the corporate story becomes a credit story. In an analysis last October, investment banker Teresa Grobecker modeled the effect of routing roughly a fifth of listings off the MLS: the direct hit to home prices looks modest, but appraisal variance widens and credit tightens through the mortgage market, where the near-term danger is a lending freeze rather than a price crash.
Thin, noisy comparable sales raise repurchase and model risk for lenders; that drives underwriting overlays, wider secondary-market spreads and slower closings. The price effect is the part everyone debates. The financing-plumbing effect is the part that has gone almost unexamined — and it is the one that should worry banks and their regulators.
Before it, housing resembled a car lot, where the dealer knew cost and comparable sales while most customers didn’t, and price was less discovered than extracted. The MLS pulled American housing toward something closer to a transparent exchange — everyone seeing the same data, any agent able to sell any firm’s listing. Walling off inventory runs that backward, handing the advantage to whoever controls the listings.
None of this makes Zillow a disinterested party; it is a powerful company defending a business built on open access to listings. Nor is it the only one now sounding the alarm: On July 1, the Consumer Federation of America petitioned the FTC and the Department of Justice to investigate these MLS partnerships, warning they “increase steering incentives” and let a firm “make money on both ends of the transaction.”
But on this question the public interest and the soundness of the lending system align. A complete, honest record of what homes sell for is infrastructure — closer to a stock exchange’s trade tape than to any one company’s product.
Regulators and bank supervisors have spent years worrying about opacity in markets far less central to household wealth than this one. They should look past the corporate fight to the thing it obscures: the data the mortgage system quietly depends on is being privatized, one listing at a time.
Bruce Ailion is an Atlanta real estate broker and attorney with a master’s degree in real estate. He competes with Compass and other firms that advocate privately marketed listings.
This column does not necessarily reflect the opinion of HousingWire’s editorial department and its owners.
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