For economists, presumed consent is just one of a number of good ideas for boosting supply to match demand. Most involve money.

One argument against presumed consent is that it isn't real consent. Andrew Oswald of the University of Warwick wants to use money to make it real.

He has suggested that each year's British income tax form include a box that taxpayers can tick to unequivocally grant authorities the right to harvest their organs after they die. In return they would get a small tax deduction. Oswald guesses that as little as 10 UK pounds or $A20 would do the trick. Most of us are surprisingly amenable to small bribes.

In Australia such a scheme would cost less than $200million, chickenfeed compared to the billions the Government spends annually on a private health insurance rebate that as far as anyone knows doesn't save a single life.

It would save the Government money as well. It wouldn't need to buy all those dialysis machines. The net cost to Federal Treasurer Wayne Swan's budget could be close to zero.

If you want to keep money out of it, economists can help there as well. Alexander Tabarrok of George Mason University sees the whole thing as a trade: I agree to give you something after I die if needed, in return for you agreeing to give me something after you die. But he says if there's no trade, there should be no deal.

His slogan would be "no give, no take". Spare parts would be available only to people who had signed up some years before to donate their own. A less severe rule would move people who had previously signed up as donors to the top of the queue. It would motivate me.

And then there's live trade. Most of us have two kidneys. We only need one. If I sell a kidney I don't need to someone who has none in return for money, both of us have been made better off, probably a lot better off. Economists call this a gain from trade.

It is true that I would be taking a risk in order to earn the money. But people take risks in return for money all the time, construction workers on building sites and coal miners among them. Most of the time we don't seem to mind.

In any event, the risk of dying from such an operation is small apparently about the same as the risk of dying during cosmetic surgery.

Doctors are naturally resistant to the idea of removing kidneys from healthy people. Their oath requires them to do no harm. But they are already taking kidneys from healthy brothers, sisters, wives and husbands who donate their organs out of love.

All that the Nobel Prize-winning economist Gary Becker proposes is that they also do it for people who sell their organs for money.

If you find the idea abhorrent you are in good company at the moment. But our idea of what is abhorrent changes over time. Once it was widely regarded as abhorrent to lend money for interest. Life insurance (where I make a bet that my loved one will die early) was similarly regarded as beyond tasteful.

US economist Virginia Postrel argues that by restricting living donations to friends and family (and sometimes helicopter pilots like Kerry Packer's) we are discriminating against people who don't have friends or family.

She means it. Two years ago she donated one of her kidneys to an acquaintance because she knew no one else would. She says it would have felt better if money had changed hands.

She has an answer, too, for people who say that the poor would be the most likely to lose their organs in a legal trade in living kidneys, creating a one-way traffic in body parts to the rich.

She says we could give anyone who donated a living kidney a one-year tax holiday. That's not worth much to a poor person, but it's worth an awful lot to a rich one. "Suddenly all of the founders of Google would be lining up," she says.

They are ideas worth taking seriously. What's happening now is an appalling needless tragedy.

While writing this article I logged on to www.australiansdonate.org.au and typed in my Medicare number. I'd signed up as a donor within 45 seconds.

Peter Martin is Economics Editor.

peter.martin@canberrati mes.com.au