THIS year marks the 200th anniversary of the first successful human-to-human blood transfusion, conducted by James Blundell, an English obstetrician working just across the Thames from The Economist’s offices. Today blood is big business—with global exports worth more, in 2016, than global exports of aeroplanes. But that trade is distorted by the refusal of most governments to allow payment to people who give plasma, blood’s yellowish liquid component.

The blood trade today consists mostly not of blood for transfusion, demand for which is falling as medical techniques improve, but of plasma (see article). Most of this comes from plasma-collection centres, where it is extracted from whole blood and the platelets and blood-cells are transfused back into the donor. Plasma is used to make drugs such as factor VIII, which helps haemophiliacs’ blood to clot, and vaccines for rabies, tetanus and Rhesus disease. Almost 50m litres of it were used in 2015, enough to fill 20 Olympic swimming pools. America, the OPEC of plasma, produces 15 of those swimming-pool equivalents. Forget steel and cars: plasma makes up 1.6% of America’s total goods exports.

The secret of this success is simple: America lets companies pay people for their plasma. So do the few other countries that are good at collecting the stuff, including Germany and Hungary. Others don’t. Big importers such as Australia, France and Belgium have banned payment. In Canada, where the issue is a live debate, the lone company trying to collect paid plasma has recently been banned in two provinces and risks the same in a third.

Blood and treasure

The aversion to paid plasma rests on three reasonable-sounding but largely groundless propositions. The first is that it is unsafe. Payment might encourage donors to conceal dangerous behaviour—such as intravenous drug use. In the 1980s and 1990s, tainted blood products infected half the world’s haemophiliacs with HIV, along with tens of thousands of plasma donors in China. But modern plasma products do not carry such risks. They are heat-treated and bathed in chemicals to sanitise them (an impossibility for blood for transfusion). Since the adoption of these techniques there has not been a single case of transmission of HIV or hepatitis via plasma products. Doctors agree that plasma products from paid donors are just as safe as those from unpaid ones.

A second argument is that, if people are paid for their plasma, fewer will volunteer to donate whole blood for transfusions. (Paying for whole blood would be unwise, since it cannot be sterilised as plasma can.) But there is no evidence that paying for plasma diminishes the supply of donated blood. That is why, in Canada, more than 30 economists and philosophers wrote an open letter arguing against bans on paid plasma. Americans voluntarily donate as much blood per person as do Canadians.

A third argument is that paying for plasma preys on the poor. It is possible that those selling plasma need the money and therefore might give too often. In America plasma donors can give twice a week; those in Europe can give just once a week. There is no evidence of harm to their health in either case, but more long-term study would be prudent.

Those against allowing payment suggest using voluntary donors instead. Yet every country that does not pay ends up importing plasma. And the fact that America is by far the dominant supplier carries risks of its own. The dependence on a single source leaves the rest of the world vulnerable to an interruption of supply. To protect their people, therefore, other governments need to diversify their supplies of plasma. Paying for it would make a big difference.