Statistical distribution of the major blood types in the U.S.:

O+   37.4%
O-    6.6%
A+   35.7%
A-    6.3%
B+    8.5%
B-    1.5%
AB+   3.4%
AB-   0.6%

The rarest blood type found is called bombay blood (subtype h-h), found only in a Czechoslovakian nurse in 1961 and in a brother and sister in Massachusetts in 1968.