Some employers report employment status/income of all their employees to private companies who keep databases. Those databases are used for this sorta thing as

Some employers report employment status/income of all their employees to private companies who keep databases. Those databases are used for this sorta thing as well as background checks. I can't remember the name of the specific database I am thinking of that I know exists, I think its owned by LexisNexis and LexisNexis advertises they have this information - https://www.lexisnexis.com/government/solutions/literature/screening.pdf https://www.lexisnexis.com/government/solutions/literature/s... You also self report your income to credit card companies.