A Vox reader asks: Why are so few people organ donors? Why would someone choose not to be a donor? Everyone agrees it’s a good thing but very few people actually do it.

Grab your ID out of your wallet. Does it have a heart on the front or back? If so, you’re one of 170 million Americans who’ve signed up to donate their organs after death. That’s about 60 percent of all eligible adults in the US — hardly “so few people.”

But if most Americans support organ donation and many have registered, why do we still have over 100,000 people waiting for transplants, with 13 people dying every day?

The gap between support and actual donations comes down to the two different ways one can donate their organs and the surprising quirks and issues particular to each.

Donating after death

First is after-death donations, where someone signs up to donate their organs after they die. The biggest bottleneck here isn’t registration — it’s medical.

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Only about three in 1,000 people die in circumstances that allow for organ donation, according to the nonprofit Donor Alliance. To remain viable for transplant, organs need continuous blood flow right up until surgical removal, which means dying in a hospital, on a ventilator, typically from brain death, with your heart still beating through mechanical support.

When someone dies at home or in an accident without immediate medical care, crucial organs like kidneys, liver, and heart........

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