[meyer]

Folks who have the capacity to be millionaires and the ability to control how much they earn will probably figure out how to manage income to keep it below the radar.

Definitions aside, that is exactly what people will do. We see millions work part-time or for part of the year (at least 'on the books') so that they can continue to collect "earned income credit" or state-sponsored unemployment benefits. There is no reason why someone at the higher range of the income scale wouldn't do similar to minimize their tax burden.

[Myrddin]

I'm pretty sure what is meant by "millionaire" in this context is an annual earned income exceeding a million dollars. Lots of folks achieve a net worth over a million. That was commonplace in southern CA when real estate values skyrocketed. A few folks actually sold in time to realize the appreciation. The house where I grew up was purchased for $19,000 in 1962 and sold for $512,000 in Oct 2005.