David Glickman should be busting his buttons with pride. His telecom company Ultra Mobile is ranked No. 1 on theInc. 5000. In 1998, Glickman’s first telecom venture, Justice Technology, took the top spot. And in 2010 another Glickman telecom business--Hometown Telecom--landed at No. 81.

A remarkable achievement, obviously. But less remarkable than if Glickman had followed up his Justice Technology triumph with companies that made digital advertising platforms or Fair Trade coffee or socks.

In March, New York University’s Stern School of Business released a study that demonstrates something most people know intuitively: Serial entrepreneurs fare better when they stick to their knitting. Startup founders benefit from the experience gained running a prior business in the same industry, even if that prior business failed. “Leveraging your industry-specific knowledge from one venture to the next can be incredibly valuable,” says J.P. Eggers, an associate professor at Stern.

Glickman clearly found that to be true. And so have at least two other entrepreneurs who made it to No. 1 and--in different years--placed companies elsewhere in the ranking.

If you’re ever on Jeopardy and are presented with the answer “He invented the three-digit security code on the backs of credit cards,” just respond “Who is Tim Litle?” and you will be correct. Litle--active in direct marketing and financial services since the 1960s--is also responsible for credit card rules that let customers buy on installment plans and the system by which mass mailers get discounts if they presort their missives. One can be an industry titan without being a household name.

Litle first made the Inc. 500 at No. 16 in 1992 with an electronic-payments processor for catalog companies called Litle & Co. He sold that business to First USA in 1995 for $80 million. But First USA did not buy the name (the business is now part of Chase Paymentech), so Litle was free to use it again when he launched another electronic-payments processor in 2001. The big difference with Litle & Co. version 2 was that more than half its customers were internet retailers. Litle leveraged everything he’d learned about the business--including his dense professional network--to grow the company 5,629 percent to $55 million. It debuted at the No. 1 spot on the 2006 Inc. 5000.

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