- Before
- Validates 31 models a year and signs every fairness test record — from notebooks she has to rebuild to trust. “A number without its reason is not a test I can sign.”
- Now
- Reads a record where every number cites its run, data cut and code version, and signs it the morning the test ran.
One rating model, from the bench to a signed test record
Kestrel Point Mutual’s Personal Auto Rating Model v7.2 adds a telematics driving score and rebases the credit-based insurance score tiers. It is due in the New York rate filing on Tue 1 Dec. Here is its test, screen by screen, in the working solution.
- 01Material change
Every model in scope, with its retest trigger
Grace Liang · Model risk validatorEight models are in scope — pricing, underwriting and claims — each with its last test, its result and when it is next due. v7.2 is on the bench because of a material change: a new telematics score and rebased credit tiers. The fraud referral model has a finding open, and the homeowners pricing model is due its annual retest in 18 days.
“100% of 2026 changes tested before production.”
- 02Mon 12 Oct · 09:14
The model on the test bench
Grace Liang · Model risk validator184,260 New York quotes from April to June 2026, reference group White. Black-probable drivers reach the preferred tier at 30.1%, White drivers at 41.8% — an outcome gap of 11.7 points against a threshold of 8.4. Four of the six tests fail: adverse impact ratio 0.72, odds ratio 1.72, standardized difference 0.24 and marginal effect 4.6% for Black-probable drivers.
“3.3 points over the threshold — Black-probable drivers reach the preferred tier at 30.1%, White drivers at 41.8%.”
- 0309:14 → 09:52
Thirty-eight minutes, every step in view
Six agentsThe Model reader reads the 148-page model documentation and finds two inputs changed since v7.1. The Group estimator places 97.6% of quotes in a census block group. The Metric runner runs six tests across three group pairs and female vs male. The Proxy detector makes 11 refits, the Alternative searcher refits five alternatives, and the Explanation writer drafts the record.
The last step is never an agent: “Grace Liang · model risk validator — reads the record and signs.”
- 04One click on a failing test
What drives the 11.7-point gap
Proxy detectorThe gap is decomposed by input: ZIP code territory carries 6.0 points, credit tier 2.8, vehicle age 1.1, prior insurance lapse 0.7. The telematics score narrows the gap. Five territories carry the territory share, and in T07 the 5-digit factor charges 31% more than the state where losses run 8% higher.
- 05Run FT-2026-114 · 09:31
Which input stands in for a protected class
Proxy detectorEach of the 11 rating inputs is removed in turn and the portfolio re-scored. ZIP code territory predicts Black-probable membership with an AUC of 0.81 on its own; removing it closes 51% of the gap but costs 3.6% of the lift. Telematics, at 0.51, is not a proxy — removing it widens the gap slightly.
“Removing it closes 51% of the gap but calibration for Black-probable drivers falls to 0.93, so the input should be replaced, not removed.”
- 06What-if
Switch ZIP code off, and watch what breaks
Grace Liang · Model risk validatorOn the bench, ZIP code territory is switched off and all 184,260 quotes re-scored. The gap falls to 5.7 points, under the 8.4 line, and five of six tests pass. But calibration for Black-probable drivers drops to 0.93 and the model keeps only 96.4% of its lift — below the 98% the testing standard requires.
- 0709:44
Five fairer alternatives, side by side
Alternative searcherFive candidates are refit on the same quotes and put through the same six tests. Removing ZIP and credit together closes the most but keeps only 91.5% of the lift. The density-banded territory — county by five population-density bands — passes six of six with a 7.3-point gap and 99.3% of the lift. Mean premium for Black-probable drivers falls $71; 9,412 quotes change tier; the overall rate level is unchanged.
Kept only if it holds at least 98% of the model’s lift. The agent proposes; it never adopts.
- 0810:12
The model owner adopts it for the filing
Nadia Ferreira · Pricing actuaryNadia adopts Personal Auto Rating Model v7.2-DT for the New York filing on Tue 1 Dec 2026, effective 1 Mar 2027. The test record is redrafted on the spot — sections 6 and 7 — and goes to Grace to sign.
- 09Drafted
A test record with every number cited
Explanation writerFourteen pages and 63 citations: why the test, the data and group estimates, the results as filed and density-banded, what drives the gap, the alternatives, how each input relates to risk and the decision. Every number points to its run, data cut and code version in the margin — the circular letter, the model documentation, the loss study, the testing standard.
“Territory: claim frequency rises with traffic density and theft; loss cost by density band is monotone, 0.86 to 1.18 — replace with density bands.”
- 10Signed · 10:41
The validator signs, and the record is sealed
Grace Liang · Model risk validatorGrace confirms she has read every section and its sources, that the tests ran on the version being filed, that the alternatives search is documented and that group estimates stayed in the test environment — then signs. The record is sealed with its data cut, code version and run log, and one more click sends it to Marcus Odell in compliance for the rate filing packet. Helen Ashworth’s annual attestation picks it up on 1 Dec.