Do you have a link or reference for the 10% of all personal income figure? Are you using NI less corporate income?
You could go here:
http://yale1962.org/speakout/?p=41
“Laffer: I think we go the route of tax reform. I mean, there was a great article in The Wall Street Journal today, by the way, that went on tax reform, and it was really terrific. I think we go tax reform. We get a low-rate flat tax. I like the one that Jerry Brown did in 1992 when he ran against Clinton in the primary. You get rid of all federal taxes except for sin taxes and put two low-rate flat taxes, one on businesses–net sales or value added–and one on personal unadjusted gross income. No deductions, no exemptions. Just bang, that’s it. And you could match all federal revenues today with a tax rate of about 11.5%. That’s pretty amazing. We could really have this economy booming.”
But I’ve confirmed that by using the IRS website tax statistics: http://www.irs.gov/pub/irs-soi/08db01co.xls
Where you can see that the Net Collections (Gross minus Refunds) of Corporate Income Tax was $301B for 2008 while the Net Collections of Personal Income Taxes was $1,060B for a total Income Tax collected of $1.36T for 2008.
Total Income is tougher because the IRS doesn’t even require filing of so many types, sources and levels of income. But using the BEA.gov figures for 2008 Personal Income, I got $12.4T which is slightly less than 11%. That doesn’t allow for the economic growth that would follow eliminating corporate income tax and lowering the capital gains, dividend, and marginal income tax rates. So 10% seems likely to me.