The Peril

in print · The Premium · plate i

A risky prospect is worth less than a sure one of equal average value, and the gap between them is the premium — the price of bearing what cannot be foreseen. This plate sets out that price: why the cautious pay to be rid of risk and the bold must be paid to take it on, how the certainty equivalent measures what a gamble is worth to its bearer, and how Bernoulli grounded it all in the curve of utility. It looks like the most natural of prices; the plate's argument is that even here it is not one number but a verdict — on who can afford to bear the unforeseen, and at what cost to whom.

You must wager. It is not optional. You are embarked. Blaise Pascal, Pensées, 1670

Every price so far has been the price of a thing — of labor, of land, of time. This one is the price of a shadow: the price of not knowing. A venture that might pay handsomely and might pay nothing is worth less, today, than a sure thing of the same average value, and the gap between them is the premium — the extra return that must be offered to persuade someone to bear a risk rather than avoid it. Most people will pay to be rid of uncertainty: that is why they buy insurance, accepting a small sure loss to escape a large unsure one. And most people must be paid to take it on: that is why a risky bond yields more than a safe one, and why, over the long run, the bold are richer than the cautious. The premium is the price of bearing what cannot be foreseen — and someone, always, is bearing it.

The premium hides in plain sight, wherever a reward waits on an uncertain future. It is the extra cents a junk bond pays over a treasury, the higher wage a deep-sea diver earns over a clerk, the discount at which a startup's shares trade against a utility's, the yearly sum a family hands an insurer against the small chance of ruin. In each, a party is being paid to hold a danger, or is paying to be free of one. The oldest and plainest case is the sea. A merchant who sent a ship to the Indies might double his money or lose the cargo entire, and centuries before anyone could calculate the odds, underwriters at the coffee-houses of London would, for a fee, promise to make good the loss if the ship went down. The fee was the premium in its first and literal sense: the price of another's willingness to bear what the merchant could not. The instruments have multiplied beyond counting since; the thing they price has not changed.

To say a risky prospect is worth less than its average is to say something precise. Offer a person a coin-flip between nothing and a thousand, and its average — its expected value — is five hundred; yet almost no one, asked to name the sure sum they would take instead, will say five hundred. They will take less: four hundred, three hundred, whatever figure makes the certainty as good to them as the gamble. That figure is the certainty equivalent, the sure thing the bearer holds equal to the risk; and the distance between it and the average is the premium, the discount the bearer demands for the uncertainty. A man whose certainty equivalent for the coin-flip is four hundred is, in effect, willing to pay a hundred to be rid of the risk — or must be paid a hundred to bear it. The premium is not a number in the prospect itself. It is the gap between what the gamble is worth on average and what it is worth to the one who must live with how it falls.

Where does the average itself come from? The notion that a gamble has a calculable worth is younger than one might think. For most of history chance was the province of fate and the gods, not of arithmetic; it was only in the seventeenth century that Blaise Pascal and Pierre de Fermat, corresponding over a gambler's puzzle about how to divide the stakes of a game cut short, worked out how to weigh an uncertain prospect. Their answer was the expected value: list the outcomes, multiply each by its probability, and sum. A prospect with a nine-in-ten chance of nothing and a one-in-ten chance of a thousand has an expected value of a hundred, and a bet that costs exactly a hundred to enter is, in this sense, fair. The calculus was a triumph; it turned the unforeseen into a thing of numbers. But it carried a quiet assumption — that a prospect is worth its expected value — and that assumption, it soon emerged, is false of nearly everyone.

The man who explained why was Daniel Bernoulli, in a paper of 1738. He began from a paradox the expected-value rule could not handle: a wager that pays two ducats if a coin lands heads on the first toss, four if on the second, eight on the third, and so on, doubling each time, has an infinite expected value — yet no sensible person would pay more than a few ducats to enter it. Bernoulli's resolution was to distinguish a sum of money from the good it does its owner. The satisfaction wealth brings, he proposed, rises ever more slowly as wealth grows: the second thousand pleases less than the first, the millionth far less again. If a person values not the money but the utility it yields, and if that utility climbs in a curve that flattens, then a fair gamble — equal chances at a sum above and a sum below one's wealth — must lower expected utility, because the possible gain adds less satisfaction than the equal possible loss destroys. From this single idea, the diminishing marginal utility of wealth, the whole of risk-aversion follows. The premium is the price the curvature of utility exacts.

So far the premium looks like the most honest of prices: the measure of a real cost. Bearing risk is not nothing — the loser is genuinely ruined, the variance genuinely felt — and the concave curve of utility puts a number on the discomfort, so that the premium can be calculated, charged, and earned like any other fee for any other service. But notice what the calculation has quietly conceded. The certainty equivalent, and so the premium, depends on the shape of the bearer's utility — and that shape is not the same for everyone. A price is a verdict on a hidden contest, mistaken for a fact of nature; and the price of risk, for all its mathematical dress, is not a single number written into the prospect but a different number for every person who might bear it, fixed by how much the loss would cost each one. The same coin-flip is a small thing to a man of means and a catastrophe to a poor one, because the curvature of utility is gentle where wealth is ample and brutal where it is scarce. The premium, in other words, is not read off the risk. It is read off the bearer — and the bearer's place in the world.

None of this makes the premium a swindle, and the case for it is strong. Risk does not vanish when it is ignored; someone must hold the future's uncertainty, and a society that paid nothing for the service would not get it — no one would underwrite the ship, fund the untried venture, or hold the shares whose value lurches with the world's fortunes. The premium is the inducement that calls risk-bearing forth, and the instruments built upon it are among the quiet triumphs of economic life. Insurance pools thousands of independent dangers until, by the law of large numbers, the ruin of the few becomes a calculable cost shared by all. Diversification, as Harry Markowitz made precise, lets an investor hold many uncorrelated risks so that the failures of some are cancelled by the successes of others, shedding hazard without shedding return. And the reward for bearing the risk that cannot be diversified away — the equity premium, the long historical surplus of stocks over bonds — has made patient owners rich precisely for their willingness to endure the lurching. The premium pays for something real, and the something is scarce.

Grant all of it; the difficulty is not that the premium is unearned but that it is unequal, and the inequality is not incidental. Because the price of risk is read off the bearer, the same danger is dear to the poor and cheap to the rich — and the market, indifferent to whose utility it consults, lets the cheap bearer collect what the dear bearer pays. The family that cannot survive a bad year buys insurance, takes the safe wage over the risky stake, accepts the lower but surer return; and each of these is a premium paid, a price for the safety their thin cushion forces them to want. The investor with a fortune to spare bears the matching risk at little cost to his peace, and pockets the premium the cautious surrendered. The flow is steady and mostly invisible: the price of risk runs from those who can least afford to bear it to those who can best afford to wait it out. What is sold as the reward of courage is, in part, the reward of having a cushion — and the cushion, not the courage, is what most of the world lacks.

This is what it means to call the price of risk a verdict rather than a fact. The mathematics is real: given a person's utility, the certainty equivalent is exact, the premium precisely the gap. But a price is a verdict on a hidden contest, mistaken for a fact of nature; and the contest the price of risk records is the one over who can afford to face the unforeseen and who must pay to be spared it — a contest the elegant curve of utility describes in perfect detail and settles not at all. The premium tells us, with great precision, what bearing a risk costs the one who bears it. It does not tell us why that one and not another bears it, or whether the distribution of cushions that decides the matter is just. The number is honest; the silence around it is where the argument lives. The price of the unforeseen is not a law of nature but a ledger of who, in a given order of wealth, has the means to be brave.

The premium is sold as the wage of courage; it is also, more quietly, the rent of a cushion.

The price of risk, then, is where this volume's question begins, not where it ends. We have a number for what bearing the unforeseen costs its bearer, and the recognition that the number depends on who the bearer is. What we do not yet have is an account of the bearers who are paid — the entrepreneurs and investors and founders whose fortunes are held up as the reward of nerve. For the premium, recall, is paid out only to those who bore a risk and came through; and the next plate asks what, exactly, coming through proves. The future discounted for being uncertain is the near twin of the future discounted for being late, the price of time anatomized in the volume beside this one; the curve of diminishing utility that sets the premium is the same ghost no instrument can read, treated among the quantities; and the cushion that decides who may be brave is wealth held as a stock, the reservoir from which all such courage is drawn. The price of risk is real, and it is a verdict — not on the prospect, but on the one who must bear it. The argument remains open.