THE role of small business in creating new jobs has been hotly debated. On one side, David Birch and his associates at MIT claim that firms with fewer than 100 employees account for over 70 percent of all new jobs. On the other, critics point out that Birch’s assertions imply a radical shift in the make-up of the business community-with small businesses employing an increasing share of the workforce-and no such shift has been observed.