Re: WHAT IS MOST COMMON BLOOD TYPE IN THE WORLD

Dear Natasha,

It is very difficult to find an exact figure for the "most common blood type in the world" because "in different parts of the world, the fraction of individuals with blood type A, B, O, or AB differs", as summarized in a tutorial explaining What are Blood Types? from the Genetic Science Learning Center @ the Univ. of Utah.

The relative distributions in many individual countries & regions are often fairly well-documented, as in the chart showing ABO and Rh Blood Type Frequencies in the United States from Palomar College, indicating that O+ is the most common in the U.S., followed closely by A+.  However, data reported by BloodBook on the Racial & Ethnic Distribution of ABO Blood Types indicates that there are considerable geographic & ethnic variations in this distribution.  The global Distribution of Blood Types is more easily appreciated with these nice maps from Palomar College.  Nevertheless, the data presented from this geographic analysis would appear to indicate that O+ & A+ are probably the 2 most common blood types on average worldwide, too.

I was very disappointed that I couldn't find a true numerical comparison of the average blood type frequencies worldwide for you, but the great differences in the worldwide distribution might actually be a more interesting fact.  In any case, I am fairly confident in concluding that O+ is likely to be the "most common blood type in the world".

Thank you very much for the interesting question & I hope that this answer was @ least somewhat helpful,