Which blood type is the rarest?

Within the familiar ABO and Rh system, AB negative is the rarest of the eight common blood types, occurring in roughly 1 percent or less of the population, though exact frequencies vary widely between different populations. Far rarer, however, is a blood type called Rh-null, sometimes nicknamed golden blood, in which red blood cells lack all of the Rh antigens, not just the main RhD one. Only a few dozen people in the world are known to have it. Rh-null blood is extraordinarily valuable because it can, in principle, be given to anyone with a rare Rh blood type, but it is also dangerous for those who have it, since compatible blood for transfusion is almost impossible to find. This makes the tiny number of Rh-null donors extremely precious to medicine.