Good point.
I dug around to see if I could find some more recent numbers.
I found this site, with numbers for the past few years. Unfortunately, some figures, like employment, seem to lag by almost three years. The numbers in the 2003 report for example, talk about employment numbers in 2000. By the time we get numbers to see where the trend is going now, the trend will already be old news.
Still, browsing these reports might be interesting--they have a lot of facts--and the percentage of employees who work for small businesses (around 50 percent), and the percentage of businesses that fall into that category (about 99 percent), seems to hold pretty steady.