I'm flattered by some of the speculations lower down. It's not nearly so complex. I basically asked myself a series of questions about each one until I got to a rough idea by tens. The number is then adjusted by 3% or 5% with the former marking "just shy/north of" and the latter "between". If my anxieties, both about the event and not wanting to put direct bias pressure on the number, seem satisfied, I go with it.

Reinsurance got 6% because I thought "a bit more than zero" then "more than that".