Compass Called Out a '$5,590 Zillow Tax.' The Math Doesn't Hold Up.

Compass released research this week claiming that sellers who listed on Zillow received 1.3% less than asking price, compared to 100% of asking for homes Zillow had banned from its platform. The brokerage multiplied that gap against the median U.S. home price and labeled the result a "$5,590 Zillow tax." Within 48 hours, economists had publicly challenged the methodology on at least three grounds: sample size concerns, missing controls, and the fact that every listing in the data set came from Compass's own business. HousingWire covered the response in detail. But there is a more fundamental problem that the critics largely missed — and it is the one sellers actually need to understand.

What Compass Measured, and Why That Number Is the Wrong One

The study examined 296,966 Compass listings from January 2025 through May 2026. Of those, 806 were homes Zillow had banned from its platform. The banned homes sold at 100% of asking price. The homes that appeared on Zillow sold at 98.7% of asking. Compass called the 1.3% gap a loss sellers suffered because of Zillow.

Here is the problem: asking price is not a neutral measure of a home's value. It is a number the listing agent chose. Comparing what a home sold for against what the agent asked is not the same as measuring whether the seller got full value for their property.

Consider two identical homes, each genuinely worth $500,000. The first is listed at $500,000 and sells for $493,500 — that is 98.7% of asking, the Zillow side of the comparison. The second is listed quietly at $470,000, attracts a small pool of buyers with no portal competition, and sells for $470,000 — a clean 100% of asking. By Compass's measurement, the second seller performed better. In reality, that seller left $30,000 on the table.

The study cannot tell those two outcomes apart. Underpricing a home and then achieving full ask looks identical to achieving top market value — both register as 100%. That is not a data quality issue that more records would fix. It is a design flaw at the center of the entire analysis.

Why Off-Market Pricing Pressures Make This Worse

The distortion runs in one direction, and it is predictable. When a home is marketed broadly — on portals, syndicated across platforms, visible to the full buyer pool — price feedback arrives quickly. Strong first-weekend traffic, multiple offers, and competing buyers all signal whether the asking price is close to market reality. Agents can respond. Sellers benefit from the competition.

When a home is marketed quietly, that feedback loop is largely absent. One agent sets a price with limited market signal coming back. The rational response to uncertainty is conservative pricing — and conservative pricing produces asking-price percentages that look excellent on paper, whether or not the seller walked away with what the home was worth.

Compass is, in effect, grading a test that Compass wrote. Its agents set the asking prices on both sides of the comparison. The company then reported the score. That is not research that can tell sellers whether they got more money. It can only tell sellers how close they came to a number someone at Compass picked.

What Legitimate Research on Listing Exposure Actually Shows

There are studies that try to answer the right question — does restricting who sees a listing change what the seller ultimately gets, measured against an independent estimate of value? Zillow has published analysis comparing off-MLS sale prices to estimated home values. Bright MLS conducted a similar comparison of on-MLS versus off-MLS results. A University of Georgia study examined Dallas-Fort Worth transactions using a pricing model as a baseline and found a modest edge for full-market exposure that narrowed significantly in later years.

These studies do not all agree with each other, and the industry debates their construction. But they share a critical feature: they use an outside yardstick — estimated value, appraisal, matched comparables — rather than the seller's own asking price. Compass's study is not a rougher version of those analyses. It is measuring something categorically different and calling it the same thing.

The timing matters because listing rules are in active flux. The unwinding of the NAR's Clear Cooperation Policy has left brokerage owners, MLS boards, and association leaders making real decisions about portal agreements, listing requirements, and lawsuits. Some of those decisions are being shaped by this research.

What Sellers Should Take Away From This Dispute

If you are preparing to sell, the Compass-Zillow fight is worth watching — not because the "$5,590 tax" figure is reliable, but because the underlying debate is real. The question of whether limiting listing exposure costs sellers money is legitimate and unresolved. Different markets, different price points, and different property types may produce genuinely different answers.

What you should not do is treat the Compass figure as settled evidence of anything. A percentage-of-asking-price comparison tells you how aggressive or conservative your agent's pricing strategy was. It does not tell you whether you received fair market value.

When evaluating any listing strategy — portal-wide exposure, exclusive arrangements, delayed marketing — ask your agent to show you comparable sales data, not ask-to-sell ratios. The relevant question is: compared to what homes like mine actually sold for, what did I get? Any answer that references only the asking price is not answering that question.

If you want a baseline before that conversation, running your address through an instant-offer tool can give you an independent data point on what buyers are actually willing to pay today — no asking price required.