When Belgium changed its organ donor laws in 1986, the number of donors doubled within a decade. The trick was switching from a system which required potential donors to actively opt-in to donation, to one which presumed their consent was given unless they had explicitly opted out.
The Washington Post's Sarah Kliff writes:
The impact of a pretty small policy tweak is striking: Organ donation rates are 25 to 30 percent higher in presumed consent countries, according to a 2005 paper in the Journal of Health Economics. When Belgium instituted a presumed consent law in 1985, the number of organ donors nearly doubled within two years. A separate review study, published in the British Medical Journal last year, found similar effects for five countries that passed presumed consent laws in recent decades.
These are the sort of effects Mark Zuckerberg will be hoping to acheive with his attempt to encourage organ donations, announced earlier today. While encouraging people to post their organ donor status to Facebook will never be as strong as presumed consent, they both rely on the same mechanism: framing effects. By changing the way in which people perceive a question, we can change the answers given. In Belguim, they put the burden of effort on removing yourself from the organ list, while Facebook merely hopes to make what is a private decision a more public choice. But both enact social change without coercion - and even if Facebook has a tenth of the effect of the Belgian law, it will save almost 4000 lives a year in the UK and US.