You’ve seen the question on your driver’s license application. The language varies from state to state, but it boils down to the same thing: Do you want to be an organ donor? Check YES, and you give consent for your body to be harvested for organ upon your death. Check NO or do nothing, and it won’t happen.

But it doesn’t have to be this way—and in several countries, it isn’t. Among those is Spain, which has the world’s highest organ donation rate.

What’s the difference? Presumed consent, meaning that, unless you explicitly opt out by checking the equivalent of the NO box on the pertinent Spanish form, it is presumed that you are willing to donate your organs.

How big of a difference might this shift make? Big. Huge. According to the University of Iowa’s Sheldon Kurtz and writing partner Michael Saks, despite “[n]inety-seven percent of [survey] respondents indicat[ing] their general support for transplantation, […o]f those who expressed their support, only 43% had the box checked on their driver’s license.” As economists Richard Thaler and Cass Sunstein infer from this paradoxical statistic in their book Nudge: Improving Decisions About Health, Wealth, and Happiness (2009), “the concrete steps necessary to register as an organ donor appear to deter otherwise willing donors from registering” (New York: Penguin, p. 178).

But puzzling out the potential impact of presumed consent is not as straightforward as it may seem. For example, despite not having presumed consent the United States ranks second only to Spain in worldwide deceased donation rate, slightly ahead of France and Belgium while being well ahead of Sweden, Norway, and Austria—five countries all of whom operate under presumed consent. And although clearly the USA’s high level of pertinent infrastructure (hospitals, roads, communication, etc.) facilitates successful organ transplantation, all five also occupy the First World.

Some who study presume consent don’t regard it as being impactful on donation rates. “[T]here is scant evidence that presumed consent will be effective [in increasing donation rates],” claims Royal College of Physicians professor emeritus John Fabre. “There is no good evidence from anywhere in the world that a change in the law leads to a sustained increase in donation,” writes Chris Rudge in the British Journal of General Practice.

But those who oppose presumed consent tend to obfuscate the issue. Rudge, for example, attempts to minimize the Spanish success with semantics by noting that Spain “does not in fact operate an opting-out system—there is no register for people to either opt in or opt out,” entirely avoiding the term presumed consent despite the fact that this is how it works in Spain. For his part, Fabre bizarrely claims that “Spain does not operate a presumed consent system,” even though in the very next paragraph he notes that “Spain passed presumed consent legislation in 1979.”

Where Rudge, Fabre, and others in opposition to presumed consent legislation are correct is in their assertion that donation rates do not automatically rise where presumed consent is instituted; and that a variety of other factors influence organ donation, including educational policies and the dissemination of pertinent information, are at least partly determinative. “Previous studies have pointed out that, on average, presumed consent countries do not produce significantly higher organ donation rates,” Alberto Abadie and Sebastian Gay note in their 10-year, 22-country study for the National Bureau of Economic Research.

This is partly because not all countries with presumed consent policies automatically employ them, instead seeking affirmative consent from next of kin. But even in such cases, say Abadie and Gay, “[L]egislative defaults on organ donation may affect the consent decisions of the families, even if they are not enforced.” All in all, they say, “[P]resumed consent legislation has a positive and sizeable effect on organ donation rates [… and] may alleviate organ shortages.”

As if the difference presumed consent makes is not self-evident, it just so happens that in the USA we already have a working model of presumed consent (though technically called “routine removal”) donation: corneas. As Maryellen Liddy cites in the Fordham Urban Law Journal, as of 2011, 15 states may legally harvest corneas from decedents without explicit permission. Not surprisingly, where that policy is applied we see a dramatic increase in corneal transplants. “These statutes have been considered very effective,” posit the authors of an extensive report by the Institute of Medicine of the National Academies. “For example, substantial increases in corneal transplants occurred after such a statute was passed in Georgia: from 25 in 1978 to more than 1,000 in 1984 (National Conference of Commissioners on Uniform State Laws, 1987).”

Considering that routine removal has been ruled constitutional (see State v. Powell (1986)), it is a small step to making presumed consent the law of the land. Anyone can opt out of being an organ donor—but because most people won’t, organ donation rates in the USA would be sure to rise, reducing the limitations, suffering, and death of so many in need.