Short answer
A diminished value comparison works by estimating the same vehicle on the same date in two conditions: without reported collision history and after a documented, completed repair. Select several like-kind vehicles for each group, adjust visible differences, summarize each group, and calculate the gap. The example below is entirely hypothetical. It demonstrates the method and cannot support a real claim.
What to remember
- Comparable quality matters more than finding listings that produce the largest spread.
- Every vehicle should be adjusted toward the subject for year, mileage, trim, equipment, location, condition, seller type, and date where those differences matter.
- Clean-title repaired vehicles belong in the repaired group; salvage, rebuilt, flood, unrepaired, and unknown-history vehicles do not.
- A median can limit one outlier, but it cannot repair a biased sample, unverifiable history, or invented adjustment.
- Retail listings, dealer offers, wholesale results, and completed sales should be separated or reconciled because they measure different market contexts.
What vehicle is being valued in this example?
A real analysis would verify the VIN, exact trim, drivetrain, factory options, mileage, title and ownership, prior history, repair completion, and market area before searching. The final repair invoice would identify the completed work; it would not dictate the value difference.
How should potential comparables be screened?
Start narrow. Widen one dimension at a time only when the market is thin, and record why. The report evidence guide explains the full audit standard.
| Dimension | Prefer for this subject | Exclude or explain carefully |
|---|---|---|
| Vehicle | Same generation, trim, body style, and all-wheel drive | Different powertrain, base or premium trim, two-wheel drive, or a different generation |
| Mileage | A tight band around 31,200 miles | A large mileage gap without a market-supported adjustment |
| Location and date | Same regional market and observations near June 30, 2026 | Distant or stale listings combined without explanation |
| Condition | Retail-ready vehicle with ordinary wear | Mechanical faults, fleet wear, unrepaired damage, or unusually pristine condition |
| History | No collision reported in the sources reviewed for the clean group; documented repaired collision and clean title for the repaired group | Unknown history, salvage, rebuilt, flood, unrepaired, or auction-only damage |
| Seller and price | Comparable seller type and a traceable asking or transaction context | Mixing retail asks, wholesale auctions, and trade offers as if they measure the same thing |
A search result is only a candidate. Before using it, preserve the seller, URL, access date, asking price, mileage, equipment, location, title status, history statement, and a screenshot or PDF. A vehicle moves into the table only after its group is supported.
How would the clean-history comparison set work?
Assume three retail listings were verified as clean-title vehicles with no reported collision history. Each adjustment converts the listing toward the hypothetical subject. A superior comparable generally receives a downward adjustment; an inferior one generally receives an upward adjustment.
| ID | Vehicle and mileage | Asking price | Net adjustment | Adjusted price |
|---|---|---|---|---|
| C1 | 2022, same trim/AWD, 29,800 miles | $29,400 | −$200 for lower mileage | $29,200 |
| C2 | 2022, same trim/AWD, 33,100 miles | $28,700 | +$300 for higher mileage | $29,000 |
| C3 | 2021, same generation/trim/AWD, 27,900 miles | $28,900 | +$100 net for year and mileage | $29,000 |
The adjusted clean indications are $29,200, $29,000, and $29,000. Their median is $29,000 and their narrow range is $29,000 to $29,200. A real report would explain how the mileage and model-year adjustments were derived rather than merely label them reasonable.
How would the repaired-history comparison set work?
Now assume three different retail listings were verified as clean-title, roadworthy vehicles with completed collision repairs. The available records describe repaired collision history; none is salvage, rebuilt, flood-damaged, unrepaired, or mechanically troubled.
| ID | Vehicle and mileage | Asking price | Net adjustment | Adjusted price |
|---|---|---|---|---|
| R1 | 2022, same trim/AWD, 30,600 miles | $26,300 | −$100 for lower mileage | $26,200 |
| R2 | 2022, same trim/AWD, 34,000 miles | $25,800 | +$300 for higher mileage | $26,100 |
| R3 | 2021, same generation/trim/AWD, 29,000 miles | $26,000 | +$100 net for year and mileage | $26,100 |
The adjusted repaired indications are $26,200, $26,100, and $26,100. Their median is $26,100 and their range is $26,100 to $26,200. The close grouping is convenient for teaching, not something to expect from a real market.
How does the example become an indicated value difference?
| Calculation step | Hypothetical result |
|---|---|
| Adjusted clean-history median | $29,000 |
| Less: adjusted repaired-history median | $26,100 |
| Indicated difference | $2,900 |
The arithmetic indicates $2,900. It does not establish that an insurer owes $2,900. Asking prices are observations rather than completed-sale prices, the adjustments are simplified, and six invented vehicles cannot describe a real market. A defensible report would show the actual sources, range, outliers, exclusions, observation window, and sensitivity to reasonable adjustment changes.
This market comparison is different from the 17c diminished value formula. A formula applies preset caps or multipliers. The comparable method asks what relevant vehicles in the selected market actually show, then makes its assumptions visible.
How should a comparable analysis be stress-tested?
- 1
Recheck every vehicle's identity and group
Confirm configuration, mileage, seller, title, accident status, repair status, location, date, and source copy. One misclassified salvage vehicle can manufacture a large gap.
- 2
Test the adjustment direction
Ask whether each comparable is superior or inferior to the subject and whether the dollar adjustment is supported in the same market.
- 3
Review the range and outliers
Explain unusually high or low observations. Do not remove an inconvenient vehicle without a preexisting relevance reason.
- 4
Change reasonable assumptions
Recalculate with disputed comparables removed or plausible adjustments varied. A conclusion that disappears after one modest change needs a wider range or lower confidence.
- 5
Compare contrary evidence
A detailed dealer offer, completed sale, insurer worksheet, guide value, or newer listing may expose a factual difference. Reconcile what each source measures.
- 6
Keep claim questions outside the math
The table does not establish responsibility, coverage, standing, policy limits, release scope, deadlines, or payment.
If an insurer offers a different number, compare the two worksheets rather than trading conclusions. Identify mismatched trims, mileage, title histories, seller types, dates, and adjustments. That evidence-first response is more useful than insisting that one appraiser must be right.
Source check
Sources used for this guide
The links below support the legal, regulatory, market, or process points made above. They were checked on July 27, 2026.
- Judicial Council of California Civil Jury Instructions, 2026 edition (see CACI No. 3903J)Judicial Council of California
- VIN DecoderNational Highway Traffic Safety Administration
- Used Cars: vehicle history and independent inspectionsFederal Trade Commission
- National Motor Vehicle Title Information SystemU.S. Department of Justice, Bureau of Justice Assistance
- Automobile Insurance TermsCalifornia Department of Insurance
Quick answers
Frequently asked questions
How many comparables should a diminished value report use?
There is no universal required number. The set should be relevant and broad enough that one unusual observation does not control the result. Donut's current report standard uses at least three clean-history and three verified repaired-history comparables.
Why use the median instead of the average?
A median can reduce the influence of one unusually high or low adjusted price. It does not cure a bad sample, and the report should still show the range, outliers, and exclusions.
Can salvage vehicles be used as repaired-history comparables?
They should not quietly stand in for a clean-title repaired vehicle. Salvage, rebuilt, flood, unrepaired, and mechanically troubled vehicles may carry separate discounts that exaggerate the collision-history difference.
Are asking prices valid market evidence?
They are market observations, not proof of completed sale prices. Multiple traceable listings can be useful when their limitations are stated and when other evidence—such as offers, sales, auctions, or guides—is interpreted in its proper context.
Can dealer trade-in offers and retail listings go in the same comparison set?
Not as interchangeable prices. A trade-in offer can reflect wholesale economics, reconditioning, inventory, margin, and another vehicle purchase. Keep unlike value contexts separate or reconcile the differences before using them as support.
Does the $2,900 example apply to my vehicle?
No. Every vehicle and number in the example is invented. A real conclusion requires the exact vehicle, completed repair, prior history, valuation date, local market, verifiable sources, and transparent adjustments.