The Motive

Every good murder mystery needs a motive, and for a long while one financial instrument supplied it so reliably that novelists reached for it the way they reached for the poisoned sherry. It was called a tontine, and in fiction it runs like this: a handful of people pool their money into a fund that pays out only to those still alive to collect, so that as the members die the shares of the dead pass to the living and the pot swells for whoever remains, until the last survivor takes it all. Put a few relatives in a closed room with a fortune that grows at every funeral and the plot writes itself. Robert Louis Stevenson and his stepson Lloyd Osbourne built a comic novel on it. Agatha Christie used it. The Simpsons handed Mr. Burns and Grampa the last two shares of a wartime tontine and let Burns reach for his rifle. The tontine is the machine that turns the people around you into an inheritance.

Here is what the mysteries leave out. There is almost no record of any of it happening — comb the histories of the great tontines and you will not find survivors murdering one another for the pot. The murder-tontine is very nearly pure invention, a knife the novelists added to a thing that, in life, was among the dullest financial products ever devised. It was a way for governments to borrow money.

The scheme is named for Lorenzo de Tonti, a Neapolitan banker who adapted it from older Italian arrangements and pitched it to the French crown in 1653. The crown said no. He spent years in the Bastille and died in obscurity around 1684, some five years before France, needing money for a war, at last ran the thing he had proposed. The mechanism it used — and that England borrowed in 1693 to fight the same war — was this. You bought a share and named a life: a nominee, to whose survival your share was tied. The state paid a fixed sum each year and split it among all the shares whose nominees were still living. When a nominee died, that share dropped out and its portion was redivided among the rest, so every surviving share paid a little more, and the state's list of claimants shrank one death at a time until the last nominee was gone. It was a war chest repaid as a slowly concentrating annuity, and it worked — England's 1693 tontine, by one reconstruction, went on paying for some ninety years.

Notice that two people can stand behind a single share: the subscriber who collects the money and the nominee whose life is measured. In the fiction they are the same person. Burns and Grampa are both the investors and the last two lives, so that when one dies the other takes the pot. That collapse is the engine of the murder plot — and in the real national tontines the two came apart, which is where the whole lurid picture quietly falls down.

Underneath the reputation is a piece of cold actuarial machinery, and it is the same one that drives the annuity and the life-insurance policy sold on every high street. All three run on the arithmetic of who dies when; they only aim it differently. Life insurance pays out when you die, so the premiums of the living settle the claims of the dead and the money goes to the people you leave behind. An annuity and a tontine pay while you live, against the opposite danger — outlasting your money. The tontine does it in the barest form there is: a closed pool, a fixed total, every dead share's portion handed straight to the survivors. What arrives each year is, in the plainest sense, the forfeited shares of the nominees who did not last.

So the novelists were onto something real, and got it exactly backwards. The instrument did make one person's income climb out of other people's deaths — that much is true, and stranger than a poisoning. But look at whose deaths, in the tontines that actually existed. A national pool ran on thousands of scattered nominees, most of them children, named by strangers in cities you would never visit. The deaths that fattened your share were anonymous and unceasing, and each one moved your payment by a hair. There was no one to murder. Or rather, there was no murder worth doing: you would have to hunt down other people's nominees, children you had never met, one at a time across a whole country, to lift your annuity by a few livres. The fiction kept the tontine's morbid arithmetic and added the single thing the real instrument never had — a target. It shrank the pool to a parlour, put the other lives in the room with you, and made the knife pay. Spread across a nation, the same arithmetic left you something worse in its quiet way: a genuine, lawful stake in the deaths of people you could not name or reach or feel, a motive with nothing to point it at.

The people who understood this best were not murderers but arbitrageurs. In Geneva, bankers turned the tontine's one exploitable seam into a trade. Since a share could be named on any life, they stopped naming their own and went hunting for lives built to endure: girls of five or six, from families with long-lived grandmothers, who had already survived the smallpox. They bought French shares by the dozen on these hand-picked children — the demoiselles de Genève — and held them. The girls stayed home in Geneva; the money came from Paris and rose, year on year, as the crown's other nominees, the ordinary unchosen children of France, died at their ordinary rates all around them. One such girl might live into her eighties, and for eight decades a line in a French ledger would pay her Genevan owners a swelling sum every time some other child, somewhere, failed to wake. The crown had priced its tontines on how long people generally live, and was bled, slowly and lawfully, by men who had simply gone and found the ones who live longest.

That, and no murder, is what killed the tontine. Adverse selection ate it from the inside, while the honest cousin of the same idea — insurance, the ordinary annuity, longevity pooled by a company that carried the risk and kept a reserve — matured alongside it and did the same work without the closed pool and its slow, grim narrowing. The instrument with the murderer's reputation died of arithmetic and better competitors: of being outsmarted, and of being outgrown.

And now they want it back. Economists who study how to pay for old age have rediscovered the tontine and judged it, on paper, close to ideal — a way to insure against living too long with no insurer in the middle taking a cut, the mortality of the group flowing straight to the survivors as income. A few real funds run on the principle again, under milder names. The murder was always fiction and stays fiction; the reformers are right that no one is hurt. But the thing at the center of it does not disappear when you make the pool large and the payments diffuse. Your pension would be funded, in part, by the deaths of the others in your pool, and it would rise as they thinned, and you would never learn which of them it was. The tontine's oldest and truest feature is not a crime. It is a small, permanent, actuarially sound interest in the mortality of strangers, held for you, in your name, with nothing you could do about it if you tried. The novelists asked whether a man would kill for such a thing. The duller and harder question is whether he can be handed it — quietly, lawfully, for the rest of his life — and feel nothing at all.