Credit reporting agency Experian has commissioned a poll of US consumers on ID theft:
Personal Credit Index
The latest Experian-Gallup Personal Credit Index finds that roughly one-in-six American consumers (18%) report being victims of identity theft, with younger adults at greatest risk. 25% of people under age 30 report having their financial information stolen, compared with about 18% of respondents ages 31 to 64, and just 11% of people 65 and older.
The poll also finds some significant regional differences. Only 12% and 15% respectively of people in the Midwest and South report being victimized, compared with 20% and 26% of people in East and West...."
Given the uncertainty over what "ID Theft" means, I'm not sure that self-reported instances of ID theft can be considered to be consistently reliable.