Risk aversion is a straightforward name for the psychological fact that humans are often willing to pay a premium for certainly, or at least for limiting the zone of uncertainty. Suppose you, dear reader, appear on a television game show. The master of ceremonies says to you, "I can give you a nice crisp $100 bill right now!" You say, "oh, goodie." "Or!" he continues with a dramatic flourish, "I can flip a coin. If the coin comes up tails, you'll get nothing. If the coin comes up heads, you'll get $200." Let us suppose there is no element of what finance types call "counter-party risk" here. Your counter-party is the emcee. We'll assume he is entirely trustworthy and that there is nothing tricky about the coin flip itself. The expected value of the coin flip, in simple arithmetical terms, is ($200 + 0) ÷ 2 = $100. The value of the payoff if you reject the coin flip is, again, $100. So you should o...