It’s not from polling. It’s from the Social Security Administration. I gave a better link in a different fork of this comment thread.

Edit: It’s for USA and anyone who applied for an SSN. So everyone but some off-the-grid nutters.

Data Source

All names are from Social Security card applications for births that occurred in the United States after 1879. Note that many people born before 1937 never applied for a Social Security card, so their names are not included in our data. For others who did apply, our records may not show the place of birth, and again their names are not included in our data. All data are from a 100% sample of our records on Social Security card applications as of March 2024.