Including birth year helps significantly. Assuming an even distribution of birth...

arohner on Aug 30, 2011 | parent | context | favorite | on: 87% of the U.S. Population are uniquely identified...

Including birth year helps significantly. Assuming an even distribution of births, you'd expect 54000/365 ~ 148/day. Then knowing gender lets you cut that in half. Dividing again by the age distribution of voters gets that down to a reasonable number.