Leonid Hurwicz is not only the oldest man to receive the Nobel memorial prize in economics, he is the oldest person to win a Nobel prize of any sort. Here is Hurwicz on his work:
I tried to see how one could formalize the incentive issue. Initially I was thinking of it in rather informal terms, somewhat along these lines: Let us say a country has some economic problem, for instance its balance of payments is in bad shape, as in pre-war Poland. What would it do? It might, say, introduce exchange controls (you must not export money, and so on). But what happens then? People figure out ways of exporting money: one has an uncle in London, others over-invoice or under-invoice… all the usual tricks. You could of course put them in jail or shoot them. But that is a distinct failure of economics, isn’t it? Because what economists should be able to do is to figure out a system that works without shooting people.
Read the whole article, by the ever-excellent David Warsh.