My post, with a supporting IRS link, exposes this assertion as conjecture. You are welcome to research the federal and state taxation entities for raw data and statistical breakdowns of compliance rates for ITIN filings. The "illegal" aspect that is highlighted by many anti-immigration people here boils down to whether a person is a W-2 serf, a 1099 contractor, or a W-7 filing alien. This distinction feeds upon the emotions of the people that are in those classifications. Some are so bold as to propose mandatory citizenship requests, so as to swell the ranks of the W-2 group. And with respect to social security, it is a cradle to grave welfare program. Many staunch conservatives believe in privatization and opt-out rights. Those here that are opposed to immigration are simply advocating protection of a welfare program that big-spending government has over-leveraged. We should consider carefully whether we want our legislative body to make any filing status a felony offense.