Transfers to other counties

Same detector code, same 15 m match rule, same operating point — pointed at two counties it was never tuned on.

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recall

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false-alarm

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precision (raw)

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precision @ Maricopa base rate

Recall transfer is mixed. It held almost exactly in Sarasota, FL — 37.89% in Maricopa to 37.03%, a 0.86-point drop with zero retraining — but fell substantially in San Diego, CA, down to 26.91%, an 11-point drop.

Precision does not transfer at all. It depends on how common pools already are in that county (the base rate), so San Diego's raw 70.81% becomes 74.09% once adjusted to Maricopa's 22.7% base rate for a fair comparison — still 19.93 points below Maricopa's own number.

Resolution wasn't the reason for San Diego's gap. Degrading the Maricopa quad from 0.3 m to 0.6 m in place cost only 0.31 points of recall — a controlled test that ruled out the obvious explanation.

Source: the same detector and scoring code run against each county's own public parcel records, unchanged between counties, 2026-07-26.