[1] "If you lack an antigen that 99 per cent of people in the world are positive for, then your blood is considered rare."
[2] "If you lack one that 99.99 per cent of people are positive for, then you have very rare blood."
Surely the author is saying the same thing here?
"Rare" = 99 in 100 people have this antigen, while you do not.
"Very Rare" = 9999 in 10000 people have this antigen, while you do not.
That's all it says.
If you lack an antigen, but at least 1 in 100 other people also lack this antigen, then your blood is only of the "Rare" category. If you lack an antigen and you'd have to go through 10 000 other people to find someone else lacking this antigen, your blood qualifies for the illustrious title of "Very Rare".
Rare is 1 in 100, very rare is 1 in 10000.
[1] 1 in 100 --> rare
[2] 1 in 10,000 --> very rare
Long day
thanks.