In the US, more than 100,000 people were estimated to be on the waiting list for kidney transplants in 2010 – waiting lists were eliminated in Iran in 1999.
Hippen has pointed out that "since 1999, more than 30,000 US patients with kidney failure have died waiting for an organ that never arrived".
Arguing in favour of allowing people to sell their kidneys, Sue Rabbitt Roff, a senior research fellow at the University of Dundee, said last year that it was time to "pilot paid provision of live kidneys in the UK under strict rules of access and equity".