France began to use a new opt-out system of organ donation on Jan. 1, making it one of a large number of European nations that now use a “presumed consent” system. This means that any adult who dies will now donate their organs by default, regardless of their survivors' wishes, unless they have signed a refusal registry in advance. The new law gets around what has historically been a stumbling block for organ donation: the surviving families of the deceased. A survey in France previously showed that while up to 80 percent of the population was in favor of donating their own organs, about 40 percent of families refuse when pressed to make the choice. The law, which was passed last year, creates a national refusal registry, where about 150,000 of France's 66 million had signed up already. In France, there were about 19,000 people on organ donation waiting lists as of April of last year when the law was signed.

That very small percentage of opt-outs is just the beginning of course, but it's telling, too. Studies show that opt-in countries have far lower rates of donors than those who go opt-out. In countries with opt-in organ donation, such as the United States, organ donation rates vary wildly. In the US, it's about 45 percent overall, though there are massive differences according to state: In Alaska, more than 80 percent of adults are registered organ donors, compared with just 12.7 percent in New York. But many other countries with opt-in organ donation have even lower rates of sign up: In the United Kingdom, less than one-third of the population are donors, though more than 90 percent say they support it. By contrast, other opt-out European countries see rates around and above 90 percent.

Each year, in the United States thousands of people die waiting for organ donation, and there's currently a waiting list of nearly 120,000 people. Several organizations, like the American Kidney Fund, are in favor of an opt-out system.