Three words on your decision letter tell you whether you won
The Cook County Assessor's reasons follow a pattern nobody documents. "This is due to" is a denial 100% of the time. "This is the result of" is a reduction 98.4% of the time.
When the Cook County Assessor decides your appeal, the decision arrives with a stated reason. The reasons are drawn from a fixed list and are written in a formal register that gives very little away on first reading:
"This is a result of a market analysis of your property as well as an analysis of comparable properties."
"This is due to your property's uniformity with comparable properties."
Those two sentences look like near-identical bureaucratic boilerplate. They are not. Across 1.79 million decided appeals, the opening phrase of the reason predicts the outcome almost perfectly — and as far as we can tell this has never been written down anywhere a homeowner would find it.
The pattern
| Reason begins… | Decisions | Share reduced |
|---|---|---|
| "This is due to …" | 175,049 | 0.0% |
| "This is the result of …" | 124,553 | 98.4% |
| "This is a result of …" | 1,424,977 | 19.8% |
| "This result is based upon …" | 59,596 | 10.3% |
Read that table again, because the first two rows are remarkable.
"This is due to" appears on 175,049 decisions. Not one of them was a reduction. Zero point zero percent.
"This is the result of" appears on 124,553 decisions, and 98.4% of them were reductions.
The difference between a denial and a grant is, reliably, the difference between due to and the result of. One word — the definite article — separates the two most common phrasings.
Why this happens
We should be careful not to over-read this. The Assessor is not encoding a secret. What is almost certainly happening is that the office's reason codes were written in two families, and the grammar follows the logic of each.
A denial explains why the assessment stands: it is due to something about your property or your evidence. "Due to your property's uniformity with comparable properties" means, in plain words, we checked, and you are already assessed in line with your neighbours, so there is nothing to correct. It reads like a refusal because it is one.
A grant explains what the new value is: it is the result of an analysis the office performed. "This is the result of a sale analysis of your property" means we looked at the sale and changed the number.
The generic middle case — "this is a result of a market analysis of your property as well as an analysis of comparable properties" — is the workhorse phrase, used on 1.4 million decisions and reduced 19.8% of the time. It is close to the county-wide average because it is applied to the ordinary run of appeals in both directions.
The reasons in full, and what each one means
| Reason given | Decisions | Reduced |
|---|---|---|
| A result of a market analysis of your property as well as an analysis of comparable properties | 1,424,549 | 20% |
| Due to income, market or cost analysis supporting the assessment | 80,587 | 0% |
| Based upon consideration of the appraisal submitted and an analysis of recent sales | 50,206 | 0% |
| The result of an income, market or cost analysis | 46,796 | 100% |
| Due to an analysis of the sale of the property | 41,856 | 0% |
| The result of a sale analysis of your property | 38,821 | 100% |
| Due to an analysis of the actual sale transaction of the property | 26,171 | 0% |
| The result of the partial occupancy of your property | 13,878 | 100% |
| Due to your property's uniformity with comparable properties | 11,762 | 0% |
| Due to insufficient data having been submitted for our review | 7,956 | 0% |
| The result of the total vacancy of your property | 5,262 | 100% |
What each denial is actually telling you
The value of knowing which phrases are denials is that the rest of the sentence then tells you why, and that determines whether appealing again is worth anything.
"Due to your property's uniformity with comparable properties." The office ran the uniformity comparison and concluded you are in line with your neighbours. If you filed a uniformity argument, they have answered it directly. Re-filing the same argument at the Board of Review without different comparables is unlikely to go anywhere; you would need either better comparables or a different ground entirely.
"Due to an analysis of the sale of the property." You have a recent sale on record and the office is using it against you. This is the hardest denial to overturn, because a recent arm's-length sale of the subject property is the strongest evidence in the process and it is pointing the wrong way. The exception worth checking: whether the sale was genuinely arm's length. A transfer between relatives, a foreclosure, or a sale that included personal property is not the same thing, and correcting the record is a real argument.
"Due to insufficient data having been submitted for our review." This one is the most encouraging denial you can get, because it is not about your property at all — it is about your filing. The office is saying it could not evaluate the claim on what you sent. 7,956 appeals were refused on these grounds. If yours was one, the substance of your case has not been rejected; it has not been heard. Fixing the submission and re-filing at the next stage is a genuine option.
"Due to income, market or cost analysis supporting the assessment." Usually seen on commercial and income-producing property. The office ran the income approach and it supports the current number. To move it you need to challenge the inputs — the rent roll, the vacancy assumption, the capitalisation rate — rather than assert a different conclusion.
The grants tell you something too
Two of the reliable-grant reasons are worth noting because they point at arguments many owners never think to make.
"The result of the partial occupancy of your property" — 13,878 reductions — and "the result of the total vacancy of your property" — 5,262 reductions. Vacancy and partial occupancy are recognised grounds, they are granted essentially whenever established, and they are invisible to any argument based on comparable sales. If a building sat empty or part-empty for a meaningful part of the year, that is a distinct claim with a very high success rate, and it does not compete with a uniformity argument — it is a different question.
"The result of a sale analysis of your property" — 38,821 reductions, 100% of the time. The mirror image of the denial above. Where your own recent sale price is below the implied market value of your assessment, it is close to decisive. The subject property's own arm's-length sale is the one piece of evidence that is about your house rather than about houses like yours, and the record shows the office treats it that way.
A caution about reading too much into this
This pattern is descriptive, not a rule the office has published. It holds across 1.79 million decisions spanning six tax years, which is a very large sample, but it describes how reasons have been worded historically rather than a commitment about how they will be worded next season. Reason code lists get revised.
It also only covers the Assessor. The Board of Review is a separate body, reached after the Assessor, with its own procedures and its own record. Nothing here tells you how the Board words its decisions.
And a denial is not a judgement about your property's worth. It is a judgement about the argument you made, on the evidence you sent, at one stage of a multi-stage process. The most useful thing this dataset shows is how often the door is left visibly open — "insufficient data" is not "you are wrong", and nearly eight thousand owners a cycle receive that answer without realising it is an invitation.