The National Association for the Self-Employed (NASE) reports that home-based businesses are on the rise in the United States:
As technology increases convenience, more and more self-employed have opened or moved their business into their own homes, giving them greater flexibility and control over their professional and personal lives. According to newly released U.S. Census data, 4.2 million Americans worked from home in 2000, a 23 percent increase from the number of home-based workers in 1990.
The NASE site has more statistics on home-based businesses here. The statistics are somewhat useful — although they are getting a little long in the tooth. Maybe the NASE needs to commission a study and get some updated statistics on this growing segment of the small business community (hint hint, all you market researchers out there).