Paul Krugman explains just how regressive Bush's "progressive indexing" would be:

Workers earning 60 percent more than average, the equivalent of $58,000 today, would see benefit cuts equal to almost 13 percent of their income before retirement. But above that level, the cuts would become less and less significant. Workers earning three times the average wage would face cuts equal to only 9 percent of their income before retirement. Someone earning the equivalent of $1 million today would see benefit cuts equal to only 1 percent of pre-retirement income... It's an adage that programs for the poor always turn into poor programs. That is, once a program is defined as welfare, it becomes a target for budget cuts. You can see this happening right now to Medicaid, the nation's most important means-tested program. Last week Congress agreed on a budget that cuts funds for Medicaid (and food stamps), even while extending tax cuts on dividends and capital gains. States are cutting back, denying health insurance to hundreds of thousands of people with low incomes. Missouri is poised to eliminate Medicaid completely by 2008. If the Bush scheme goes through, the same thing will eventually happen to Social Security. As Mr. Furman points out, the Bush plan wouldn't just cut benefits. Workers would be encouraged to divert a large fraction of their payroll taxes into private accounts - but this would in effect amount to borrowing against their future benefits, which would be reduced accordingly. As a result, Social Security as we know it would be phased out for the middle class.