Does hiring someone to appeal your property taxes help? Six years of data say it is not settled
Attorneys and agents commonly take a third of the first year's saving. Across 1.79 million Cook County decisions, the advantage over filing yourself changes sides from year to year.
The property tax appeal industry runs on contingency. A firm files on your behalf and takes a share of what you save — commonly a third of the first year's reduction, sometimes half. The pitch is that professionals know the process, know the assessors, and win more often than you would alone.
It is a reasonable pitch, and it might be true. The Cook County Assessor records whether each appeal was filed by an agent or by the owner, so for once the question is answerable from evidence rather than from marketing.
The answer is more interesting than either side would like: it depends which year you ask, and the advantage changes sides.
Six years, side by side
| Tax year | Agent success | Owner success | Difference |
|---|---|---|---|
| 2021 | 33.0% (324,769) | 25.0% (48,857) | agent +8.0 |
| 2022 | 24.6% (251,800) | 25.8% (50,506) | owner +1.2 |
| 2023 | 20.9% (183,191) | 23.1% (60,224) | owner +2.3 |
| 2024 | 21.3% (367,332) | 20.9% (72,678) | agent +0.4 |
| 2025 | 15.7% (293,702) | 18.5% (68,806) | owner +2.8 |
| 2026 (partial) | 17.6% (52,120) | 23.6% (14,670) | owner +6.0 |
In four of the six years, owners filing for themselves did better. In 2021 agents did substantially better. In 2024 the two were within half a point of each other on more than 440,000 decisions.
If you pick one year, you can support almost any conclusion you like. Quote 2021 and representation looks essential. Quote 2026 and it looks actively counterproductive. That is exactly why we are showing you all six rather than the one that makes the better headline.
Why a single combined number would mislead you
The obvious move is to pool all six years and report one figure. We did that first. It gives agents 21.25% against owners 20.83% — an advantage of about four tenths of a point, on a sample large enough that the usual statistical test calls it borderline.
But that number is close to meaningless, because it averages an effect that changes direction. A confidence interval measures how much a result might move if you resampled the same underlying process. It cannot tell you anything about a process that is genuinely different from one year to the next. Reporting "agents do 0.4 points better" would take a real, unstable, year-varying difference and present it as a settled fact with a margin of error attached.
The honest summary is: on this evidence, whether representation helps in Cook County is not settled, and it has not been consistently true in either direction for six years.
What might explain the swing
We can offer possibilities, but the data does not choose between them and we will not pretend otherwise.
Selection. Agents do not file randomly. A firm on contingency has a strong incentive to file the cases it expects to win, which should push the agent success rate up. That it does not consistently do so is itself notable. Conversely, agents also file large volumes of commercial cases where the standard of proof is higher, which pulls the other way.
Composition. Agent-filed appeals are the large majority — often five or six to one — so the agent figure is close to the overall average by construction. The owner-filed group is smaller and may be self-selecting: an owner who files alone has usually noticed something specific and concrete about their own property.
The 2021 outlier. That year stands apart, with agents eight points ahead and the highest overall success rate in the series. 2021 assessments were set during an unusually volatile period, and there may simply have been more error in the roll for a professional to find.
What this means for the cost
Set the success rates aside for a moment and look at the price.
The median successful Cook County appeal reduces assessed value by 8.4%. On a home assessed at $30,000, that is roughly $2,520 of assessed value, worth on the order of $570 a year at a mid-range composite rate. A firm taking a third of the first year's saving takes about $190 of it.
Whether that is good value depends entirely on whether the firm actually raises your chance of winning — and on six years of the county's own record, there is no consistent evidence that it does. You are paying a third of the benefit for an advantage the data cannot reliably detect.
The question nobody asks the firm
If you are considering hiring someone, there is one question worth asking, and the answer is informative either way: what is your success rate in my township, and how does it compare to the Assessor's published rate for that township?
The county publishes the base rate. A firm claiming to beat it should be able to say by how much, somewhere it can be checked. A firm that cannot — or that quotes a county-wide figure well above the county's own published number without explaining the difference — is quoting itself.
What we would do
For an ordinary residential appeal in Cook County, on this evidence: file it yourself at the Assessor stage. It is free, an appeal cannot raise your assessment there, and the county's own record shows no reliable professional advantage. Spend the effort you would have spent choosing a firm on assembling better comparables instead — that is the part the record shows actually moves outcomes.
If it goes past the Assessor to the Board of Review and then toward the Property Tax Appeal Board, the calculation changes, and so does the nature of the work. Get help then, when the thing you are buying is expertise in a proceeding rather than a filing you could have made yourself.