Ever since the dot-com era, high-tech startups are more often associated with twenty-something developers. But a recent study shows twice as many technology firms are being launched by middle-aged entrepreneurs with college degrees.

Among more than 500 U.S. technology firms recently analyzed by the Kauffman Foundation, a Kansas City, Mo.-based entrepreneurship advocacy group, twice as many founders were in their 50s than in their 20s. The average age of a company founder was 39.

The study also found that more than 90 percent had bachelor's degrees, while slightly less than a third had master's degrees. Nearly half studied science, technology, engineering or mathematics, while only a third majored in business or related fields. Those who attended an ivy-league school had higher sales, with an annual average of $6.7 million, compared to $5.7 million among the overall sample.

"While education clearly is an advantage for tech founders in the United States, experience also is a key factor," Vivek Wadhwa, the study's lead researcher, said in a statement. "That a large number of U.S.-born tech founders have worked in business for many years also is important in understanding the supply of tech entrepreneurs."

Robert Litan, vice president of research and policy at Kauffman, said that knowing the age and educational background of high-tech company founders is critical to promoting entrepreneurship.