This article reports that according to a recent study sponsored by the U.S. Small Business Administration, economic factors and demographics are driving a surge in self-employment. People launching technology start-ups, minorities, women, and baby boomers are the groups primarily responsible for the growth, the study says. Data shows that the number of self-employed people over the age of 50 in the United States has jumped 23 percent since 1990, to 5.6 million workers.