So googling suggests there’s about 21 million people on the register. The uk population is about 66 million but we can rule out about a quarter of that as kids who’d need parental consent as they can’t consent themselves. Beyond that I assume we’d need to discount... who?... smokers? Drinkers? Drug users? Presumably there’s some way of cutting the 50 or so million down to the 21 or so that you’re saying we’d be lucky to get much above?
I note from searching around that in 2016 there were about 4,000 transplants from about 1,400 donors. There were over half a million deaths in 2016, so you’re clearly right in saying that the number of people dying in time, manner and place fitting for a successful donation. Only 0.28% of deaths resulted in one or more successful transplants.
The latest figures I found were 23.6 million on the registry, for July 2017. Which, apparently, is ~70% of those eligible.
Other relevant things are:
1) If possible, relatives are asked to decide
regardless of whether or not the dead person was on the register.
2) A person does not need to be on the organ donor registry for their organs to be used in transplants.
3) Last years, 37% of families refused consent to have their dead relative's organs donated.
So removing the need for a person to consent to be a donor is even more useless than I thought it was since the organ donor registry isn't crucial or even particularly important to transplants.
Some numbers directly from the NHS for the 2016/2017 year:
1413 donors.
3713 transplants.
3144 families asked to consent to organs from a dead relative being used for transplant.
1972 of them gave consent.
1172 refused consent.
So clearly removing the need for consent in order to
maybe get a small increase in the number of people on the register isn't an effective way to get more transplants done. I think consent is far more important than politicians getting a media boost and some people feeling righteous about forcing the removal of consent on other people.
Removing the involvement of families of dead people would be a far more effective way to increase the number of transplants done - that might increase transplants by as much as 37%. But it's not yet certain to be a good image move for politicians, so it won't be proposed yet.
I would guess the elderly probably are discounted as they are near end of life anyway so any organs would not likely last very long? People with health problems?
Health problems yes, elderly not necessarily. The only hard limits are 80 years old for cornea donation and 60 years old for heart valves and tendons donation (according to the FAQ on the organ donation section of the NHS website). I expect a donation is less likely to be useful from an older person, but they're not entirely ruled out.