Blood types from the most common to rare are O +, A +, B +, O -, A -, AB +, B - and AB -. Each type is determined by the presence or absence of certain antigens on the surface of the blood cells.
Although O + is the most common blood type in the United States, the percentage of people with this blood type varies by ethnicity. For example, 37% of Caucasians are blood type O +, while African Americans account for 47%, Hispanics account for 53% and 39% of Asians have this blood type. On the opposite end, the population of AB - blood types is Caucasians at 1%, African Americans at 0.3%, Hispanics at 0.2% and Asians at 0.1%.