Part 4 considers two major social issues: organ donation and climate change. Since there was significant confusion among Thaler and Sunstein’s readers after the original publication of Nudge as to their stance on organ donation, they rewrote this chapter. They state that in countries with “presumed consent,” very few people opt out of the organ donation system. On the contrary, countries where people must opt in have a far lower rate of participants. Thaler and Sunstein write, “Only 12 percent of Germans agreed to be organ donors, while more and 99 percent of Austrians had failed to opt out” (254). Though they believe increasing the number of lives saved is important, it is also important to respect the free decision of potential donors and their families.

Thaler and Sunstein relate that there are hundreds of thousands of people worldwide waiting for organs (mostly kidneys). In the U.S., “seventeen people die waiting for a transplant” every day (257). Thaler and Sunstein then go through possible policies when a potential organ donor dies. These include routine removal, presumed consent, explicit consent, prompted choice, and mandated choice. Each has a unique set of pros and cons with routine removal being the most paternalistic and aggressive approach and explicit consent occupying the opposite end of the spectrum.