Cook County's assessor quietly shifted $2.2 billion onto the wrong homeowners. Now a crop of data startups is selling the fix, one appeal at a time.
On Chicago's South Side, a brick bungalow that would sell for under $200,000 can carry an assessment that behaves as though the house is worth far more. A few miles north, in Lincoln Park or Winnetka, a million-dollar home's assessment behaves as though it's worth far less. Same county. Same tax rate. The difference isn't the neighborhood or the house — it's the number written on a form in the assessor's office. And for years in Cook County, that number was systematically wrong in one direction: cheap homes were overassessed, expensive homes were underassessed, and the gap added up to billions of dollars taken from the households least able to absorb it.
The reckoning began in 2017, when a study of more than 1.5 million residential properties — conducted by then–chief assessment officer Robert Ross with University of Chicago Harris School economist Christopher Berry and Chicago Tribune reporter Jason Grotto — documented what assessors had denied for years. Across Cook County, higher-value properties paid lower effective tax rates than lower-value ones. And the appeals process, which is supposed to be the safety valve, made it worse: higher-value properties won larger assessment reductions through appeals than cheaper homes did.
Berry kept digging. His follow-up analysis estimated that flawed assessments under Assessor Joseph Berrios shifted at least $2.2 billion in property taxes from undervalued Chicago homes onto overvalued ones between 2011 and 2015. As much as $1 billion was shaved off the tax bills of the top 10 percent of homes — single-family houses and condos worth more than $1 million on average. Because the total levy is fixed, that missing billion didn't vanish. Hundreds of thousands of other taxpayers made up the difference, and the lowest-valued homes shouldered a disproportionate share. The reporting helped end Berrios's career: Fritz Kaegi defeated him in 2018 on a reform platform.
In 2025, Berry released the scorecard. His evaluation of Kaegi's first six years, 2019 to 2024, found the administration had "dramatically reduced" the regressivity of the old system — with one wrinkle: Kaegi raised average assessments on commercial properties, but the Cook County Board of Review rolled many of those reductions back, partly undoing the shift from residential to commercial. Net result: middle and lower-income homeowners saved $1.9 billion they would have paid under the old system, and Cook County's residential assessments finally met industry standards for fairness. "Everyone — even the assessor — now agrees that the system is regressive," Berry said. "But I wanted to know how much money is at stake. The answer is easily in the billions. These dollars are being taken from some of our citizens who can least afford it and used to pay the taxes of the wealthy. It's unconscionable."
The instinct is to file Cook County as a Chicago pathology. The data says otherwise. In a paper published in the Quarterly Journal of Economics, Carlos Avenancio-León and Troup Howard documented a nationwide "assessment gap": holding jurisdictions and tax rates fixed, Black and Hispanic homeowners face a 10 to 13 percent higher property-tax burden for the same bundle of public services. Assessments move less with neighborhood attributes than market prices do, so in any city where value tracks neighborhood lines, assessments overshoot cheaper areas and undershoot expensive ones. The authors also found appeals behavior and outcomes differ by race within neighborhoods. Berry's work in Detroit helped fuel a wave of activism for reform there.
Here is the quiet scandal inside the scandal: hardly anyone fights back. Figures cited in profiles of the industry put the share of homeowners who actually appeal their assessment at roughly 22 percent, even as three-quarters say they worry about property taxes. The process is local, paper-heavy, deadline-driven, and intimidating — exactly the kind of friction that punishes everyone without time or specialist knowledge.
That friction is now a venture-backed business. Ownwell, founded in 2020 in Austin, has become the category's standard-bearer: it raised a $50 million Series B in February 2026 — $30 million in equity co-led by Alpha Edison and Mercato Partners, plus $20 million in debt — with Intuit Ventures, Left Lane Capital, and First Round Capital among its backers. The company operates full-service appeals in seven states (California, Florida, Georgia, Illinois, New York, Texas, and Washington), charges 25 to 35 percent of whatever it saves a client, and claims an 86 percent success rate in its core markets. It even publishes its own county-by-county scorecards: in Tarrant County, Texas, in 2025, Ownwell's clients with homes under $250,000 averaged $437 in net savings per successful protest, with an 80 percent success rate against a 65 percent market average.
Ownwell doesn't lack for competition. Legacy protest shops like O'Connor, Five Stone Tax Advisers, and Home Tax Shield have worked Texas for years; newer entrants include TaxProper, Owlue, and Abode Money. The pitch is always the same: the assessor's number is negotiable, and you were overpaying. There's real math behind it — lowering today's assessment compounds, because it caps how much the county can add in future years.
But there is a darker read on the appeal boom, and Berry's research provides it. The people who appeal are not a random sample of homeowners. They skew wealthier, better advised, and better resourced — the same households whose assessments were already tilted in their favor. A system where the best-informed owners shave their bills while everyone else pays sticker doesn't fix the regressivity Berry documented; it can deepen it, shifting the fixed levy back onto the households least likely to file. Berry's evaluation of Kaegi's tenure captured the dynamic in institutional form: the assessor raised commercial assessments toward fairness, and the Board of Review — the appeal body — cut them back down.
That doesn't make the industry illegitimate. It makes it incomplete. For the homeowner who wins an $800 reduction and keeps it for a decade, the appeal is the most consequential financial move they'll make all year. In the aggregate, though, the appeal industry is a private patch on a public failure — and the failure is data. The assessor's office has 1.5 million properties and mass-appraisal models; the homeowner has a hunch and a deadline. As long as that asymmetry stands, the bill on your street is partly a function of how good your data is. Companies that close that gap — for the assessor, for the appraiser, or for the homeowner — are selling the one thing the property tax system has never had: an agreed-upon number.
The category-defining name in property tax intelligence — propertytaxestimates.com — is currently available for acquisition by the firm positioned to own this space.
