Arian Foster, a running back for the Houston Texans, wants to sell shares in himself so investors can buy a portion of his future earnings. This prompts the question: why isn't there more of a market in shares in people? (No, Bowie bonds aren't quite the same thing.)

In theory, this is a trade which should benefit both parties. It would allow young people to raise money to see them through university or give them a deposit for a house. And older people could buy a stake in future income growth; the stock market, remember, does not give us this. Shares in people would also help protect equity investors from distribution risk - the danger of a shift in incomes from profits to wages.

So, why do these potentially mutually benefical trades not happen? Several answers seem to me inadequate:

"The young person would just take the money and run, or at least have less incentive to work hard." But it must be possible to contract for this problem. The Saul Goodmans surely have the wit to write a contract which steers the middle course between letting the young person leg it and committing them to slavery.

"Individuals' incomes are too risky to value accurately." In truth, though, the same is true (pdf) of corporate earnings. And the intelligent solution in both cases should be the same: to pool such idiosyncratic risk by diversifying across individuals. Such bundles of securities would give us the macro securities, for example in occupational incomes, proposed by Robert Shiller.

"All markets are prone to bubbles." But so what? If oldsters pay too much for a stake in youngsters' future incomes, this would help correct the intergenerational injustice which many believe exists in other areas.

In truth, though, there is one big investor who has for years held shares in people - the state. You can think of a big chunk of the welfare state as taking an equity stake in people; yes,libertarians have a point in claiming it violates self-ownership. It invests in us as start-ups - by spending on our health and education - and in exchange we hand over dividends (taxes) when we're earning. You can interpret the Help to Buy scheme as an extention of this; the government is making a risky investment to help young people acquire an asset.

It's often said - sometimes by me! - that the state is less innovative than markets and the private sector. However, in this context of facilitating some mutually beneficial intergenerational transfers, perhaps the state does better than the market.