From the U.S. Census
The number of U.S. residents who claim Irish ancestry. This number is almost nine times the population of Ireland itself (slightly more than 4 million). Irish is the nation's second most frequently reported ancestry, trailing only German.
The percent of Massachusetts residents who are of Irish ancestry. This compares with a corresponding rate of 12 percent for the nation as a whole. (Photo by Chicago Tribune/Nancy Stone)
Source: 2006 American Community Survey