A breakdown of those areas contributing to disposable income going back to 1948 is below. Compensation for employees and proprietors income (i.e. salaries) have decreased from well north of 80% to 70%, while personal income receipts on assets increased from less than 10% in 1948 to almost 20% in 2008 (i.e. owners of capital had been king).
And the area with the largest growth over the past 60 years? Personal current transfer receipts, which according to the BEA are:
Payments to persons for which no current services are performed. It consists of payments to individuals and to nonprofit institutions by Federal, state, and local governments and by businesses.Expect this to grow dramatically in coming years... we're all socialist now!
Update- an anonymous comment adds:
I think you're ignoring the possibility that much of this is demographic (Social Security and Medicaid). As you say, it will get worse (with the pickup in Boomer retirement).Good point.