A selected ultimate without a stated reason is hard to defend when the quarter closes.

Most reserve files still bury the decision in a notebook or a slide deck. Chain ladder, Bornhuetter Ferguson, and Cape Cod sit side by side, someone picks a number, and the memo is written later. When a reviewer asks why AY 2023 moved, the trail is missing.

numdog treats the selection as a first-class object. Methods run together. Weights are visible. The reason travels with the ultimate into the draft report.

What belongs in the reason

Name the methods that competed, the weights you chose, and what moved since last quarter. Paid development, case adequacy, and a priori changes belong in the same paragraph as the number.

ASOP 41 still puts the signature on the actuary. The system only keeps the file honest. The production run proposes; the credentialed actuary selects and signs.

What to record on every selection:

• Competing methods and the weights applied
• What moved in paid and incurred development
• Case adequacy and a priori changes
• The range that framed the selection
• Open ASOP 23 exceptions dated before methods run
• Who selected and on which valuation date

Close the loop by carrying the same reason into the reserve report draft. Do not rewrite it from memory after the meeting.

When the next quarter opens, expected versus actual starts from that documented baseline.

The question is not which method won. It is why this number, for this accident year, on this valuation date.

That is the job: a number you can explain without opening three spreadsheets.

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