In a nutshell, it would increase federal income taxes on 84 percent of all American households. Of course, and as you can expect from a Republican candidate, the 16 percent who wouldn't be affected, and who would actually get extreme tax breaks, are those who make the most money.
Households earning less than $30,000 a year would lose 16 to 20 percent of their net income, according to the Tax Policy Center's research. Those making over $200,000, however, would get to keep from five to 20 percent more.
To explain it easier, we made this nifty little chart detailing the projected changes in taxes owed by each income quintile group under Cain's "9-9-9" plan, and included the top one percent and top one-tenth of one percent in income, too.