632 QUARTERLY JOURNAL OF ECONOMICS
I.3 Information about Accident Probabilities
We have not so far discussed how customers and companies come to know or estimate the parameter p, which plays such a crucial role in the valuation formulae (1) and (2). We make the bald assumption that individuals know their accident probabilities, while companies do not. Since insurance purchasers are identical in all respects save their propensity to have accidents, the force of this assumption is that companies cannot discriminate among their potential customers on the basis of their characteristics. This assumption is defended and modified in subsection 11.1.