What is the most common blood type?

This is an average distribution of the blood types in the United States. The distribution may be different for specific ethnic groups: 

• O Rh-positive - 38 percent 
• O Rh-negative - 7 percent 
• A Rh-positive - 34 percent 
• A Rh-negative - 6 percent 
• B Rh-positive - 9 percent 
• B Rh-negative - 2 percent 
• AB Rh-positive - 3 percent 
• AB Rh-negative - 1 percent