IRS Statistics of Sole Proprietor Income

Approximately 22.7 million individual income tax returns
reported non-farm sole proprietorship profits of $244.8 billion for
tax year 2009 according to the recently released Statistics of
Income Quarterly Report. Check it out here - Summer 2011
Some other points worth noting in my opinion include: 1. For tax
year 2008, almost 67,000 foreign-controlled domestic
corporations