Turning One Kidney Into Ten


Economist Al Roth has an interesting blog post that describes how one altruistic kidney donor saved 10 lives. Here’s how it worked.

One of the things Roth has been working on, given the repugnance many noneconomists feel about paying for organs, is creating chains of organ donations. Many people who need kidney transplants have a donor who is willing to donate one, but who is not a good match for the recipient.

If you can find another couple in the same situation, it just may be the case that the two donors match the recipients in the other couple. While it is illegal to sell kidneys, it is not illegal to trade them. The catch is that the surgeries need to be done simultaneously, for fear that the couple that receives the kidney from the other pair might renege on their promise to provide the reciprocal donor kidney.

The worst part of it is that the couple that gave up the kidney now no longer has a kidney to give, meaning that they cannot be part of any future swap.

In principle, there can be long chains of such donations, but having to do the surgeries all at once gets in the way. Hospitals just can’t handle large numbers of transplants all being done at once.

That’s where an altruistic donor, who isn’t asking for a kidney back in return, becomes a critical link. If you start a chain with the altruist, then the need for the surgeries to be simultaneous is not as great. The altruist gives a kidney to a recipient. The surgery is performed. Then the donor from the couple that got the first kidney, at some other date, gives away his or her kidney to the next recipient. Because there is always one “extra” kidney in the chain, when the chain finally stops, there is no couple that has given a kidney but not received one.

Consequently, the surgeries can be done over time, rather than all at once. Eventually, one of the donors might back out, or no more matches can be made, and then the chain will come to an end.

No matter when or how it ends, the key is that there is no couple who has donated a kidney but not
gotten one back in return. So every couple still has a kidney to trade as part of some future chain.

And that is how one altruistic kidney donor, with the help of clever market designers, managed to help save 10 lives.


The big problem is that this doesn't decrease the probability of reneging enough. After getting a kidney people can "suddenly" change their mind, breaking the chain. I can easily picture myself having second thoughts, although maybe not acting on them. So the first donor, altruistic as he might be, he'd be reluctant to give a kidney away if the probability of the chain breaking is as high as I think it is, even right at the first link. What Roth's example really shows is how even tiny changes in stability of the chain can work sometimes, but for this to become a meaningful contribution to the market size one needs to be enormously altruistic -- a black swan of altruists.

Looks like there is no way around fighting the stupid repugnance. Repugnance is endogenous after all. Roth's second best solution is great, but even it has the negative externality of decreasing the incentive to push towards the first best. Why pushtowards legalizing trade if "we can build chains like these to save lives" -- never mind that the chains are unstable which makes the market practically nonexistent and Roth's solution much less relevant.



Sorry, that was very, very confusing. What is a "couple"? What does this have to do with organ sales?

The way this was written it makes it sound like someone is having one kidney removed and a new one put it but that new one will be donated somewhere else one day.

Levi Funk

To avoid reneging, you could require each recipient's spouse to simultaneously donate. Even better, put the spouse under before you put the recipient under. That should ensure a long enough chain.

Unfortunately this idea only works for those who are in a relationship or have someone close to them that is willing to give them a kidney. However, it is a wonderful way to solve the problem of being a poor match for your significant other.


A couple means a receiver with end-stage kidney disease and a healthy donor. So, A is willing to donate a kidney to B, but they are not a match. C is willing donate a kidney to D, but they are also not a match. However, A is a match to D and C is a match to B, making it possible for them to trade the organs.

The point of the chain is that if you need a kidney, you need to have someone willing to donate a kidney even if this person is not your match. Once you get your kidney, your donor will have to donate their kidney to someone else.

This way the money incentive to sell an organ is substituted by the incentive that your loved one will get a kidney if you decide to donate yours, even if you two are not a match.

It's a great idea.


This was an episode of Grey's Anatomy..

Helen Rambaut

Certainly an idea worth developing. I think all potential routes need to be developed to increase the supply of healthy kidneys.

Receiving a replacement kidney is an incredible transformation from being very sick to being healthy again.

Under a well regulated system of selecting healthy living kidney donors and committing to ther long term follow up and aftercare, I have no objection to exploring the use of the price mechanism to atttract donors.

It's a wonderful feeling to receive an altruistic donation but in practice I dont see why the donors should have to do it for free when at the same time as prolonging life they are significantly reducing healthcosts borne by the taxpayer.


Every donor after the first altruistic donor is also an altruistic donor as they no longer have a reason to donate. The initial donor makes the donation circle a line to where the intricate loop would have eventually broken, or if it hadn't broken the last person doesn't need to donate.

Presumably kidneys can't sit around for very long at all after being donated or there would be a kidney bank funded by altruistic donors, if someone you knew then needed a kidney you could trade yours in for one better suited for them from the bank.


"Every donor after the first altruistic donor is also an altruistic donor as they no longer have a reason to donate."

Not, they're not. They agreed to a contract, and they're just fulfilling their part. I think many people try follow up on their obligations even if they could get out of them without consequences. Do you not?



I'm sorry but Isn't that the definition of altruism?

Aaron Luchko


I don't think reneging would be that big a problem since people do have strong social motivations to carry through on their obligations. If one wants to strengthen the penalties even more it could be a strategy to have all the families, and some friends as well meet. If you pay a penalty in your greater social circle for reneging it becomes even more unlikely.

Aaron Luchko


Is repaying a bank loan altruism?

Sure there's no monetary cost but there's a reputation cost and a social cost to defaulting on your reciprocal promise to donate.

Altruism is when there's no cost to not performing the action.


I was initially confused by all the references to "couples" and then to #9 saying "it *is* altruism". If I'm understanding correctly, one member of each pair is agreeing to trade a compatible organ in return for their "partner" receiving a life-saving transplant. That's payment due, not altruism. And even though a court has already said such an agreement is not legally enforceable, I am sure it will one day be - not enforced as strict performance, but by financial settlement (although probably not for enough to buy a substitute organ on the black market - depending on the organ and the market, one supposes and the level of asset recovery).

The only altruism there seems to be is in agreeing to save a partner's life by giving up an organ. And since partner can be anything from blood relative to spouse to partner of any kind (drinking buddy), the degee of altruism may be graded - although there is no sure way.



@ Aaron Luchko
Wouldn't bet my kidney on that. Just pick your favorite unverifiable excuse and you are out of the chain.


So the point is that, in the absence of altruists, you are limited to cycles of donations, whereas an altruist can allow you to take advantage of shorter chains.

I fail to see how this has anything whatsoever to do with markets or economics. There was no clever market/econ trick that allowed something to happen that would not have happened otherwise. Keep in mind that the altruist is severely limited in to whom he/she can donate a kidney. So sometimes the altruist can start a cascade/chain, sometimes not, and sorry to say, economists have nothing to add to this.


That sounds like a really amazing idea. I think however though, each person that receives a kidney should sign some sort of agreement that they will donate their extra kidney after they receive their own, if they are in the healthy state to do so. HAving a sort of contract will guarentee the altruistic behaviors to continue until a person is unhealthy or unable to find a compatible recipient. This kind of action represents a peositive externality because it encourages others to act altruistically as well as society benefits from having healthy people around who can work and provide fresh ideas and solutions.


You would need a severe financial consequence for reneging after you have received a kidney for this to work. I would be interested to see whether this would be legal; it is not technically "selling" an organ but instead imposing a heavy (means tested?) fine for those who back out.

The altruistic approach is a nice idea but will result in shorter chains.


As a kidney donor, I know the testing one must go through in order to be approved to donate. It takes a while to go through those tests, and at every point you are given the opportunity to back out. It would be highly unlikely for someone to make the committment in the time and medical testing required and then get to the point of transplantation and back out at the last minute.
I gave a kidney to my grown son, but I know two other people who gave kidneys to strangers, just because they felt it was the right thing to do.


For those who are confused, the partners who give a kidney to the next couple in exchange for receiving a kidney are not being considered altruistic here. The first person to donate who has no sick "partner" is.

The whole point is not that the scheme will force people to honor their commitment, it's that thanks to the altruistic start of the chain no one gets "screwed". That is no one donated a kidney to a stranger with an expectation of saving their own partner's life and then has that deal reneged. One couple does come out more selfish and less honorable, of course.

Even if the chain is short, I would suspect that for someone willing to donate an organ to start will be pleased to have effectively saves more than one life with one organ.


Why don't a bunch of hospitals get together and build an organ donation center somewhere, where as many as 20 or 50 surgeries could be performed at once? Surely the benefits of such a place, funded by many different hospitals, and maybe even the government would be worth the cost. It saves tax payers money after all to get people in need of kidneys organs that make them healthier and get them off Medicare (which all people with renal failure get).