The Maine Angels has found itself at the top of a national ranking of elite angel investment groups.

While the Maine group, a collection of affluent individuals who pool their resources to invest in and mentor early-stage companies, is not listed in the top 20 of the overall ranking of angel investment groups, it does top the rankings of angel investment groups in another important metric, according to a national ranking by CB Insights, a research firm that focuses on venture capital, private equity and angel investment. CB Insights considered 350 angel investment groups in its report, which was released last week.

Despite competition from angel investment groups from places like Silicon Valley and Boston, Maine Angels has the best follow-on rate among angel investment groups in the country, CB Insights claims. The follow-on rate is a measurement of how many of an angel group’s portfolio companies receive additional rounds of funding.

Maine Angels’ follow-on rate is 80 percent over the past five years, according to CB Insights.

Why is the follow-on rate important? I asked Anand Sanwal, the research firm’s CEO and co-founder.

A company’s ability to raise subsequent funding is often a reflection of its quality, the quality of its prior investors/mentors and the angel group’s network, Sanwal said.

“Writing the first check is kind of easy, but if the companies all fail because they can’t raise follow-on funding, that doesn’t help anybody,” Sanwal said. “We think for early stage investors, (the follow-on rate) is an important indicator of quality.”

Sanwal confirmed that CB Insights’ measurement of follow-on rate includes any portfolio company that raises additional rounds of funding.

Maine Angels’ stellar ranking was news to Sandra Stone, chair of the Maine Angels. She tracks all the group’s investments and follow-on rounds, but she didn’t realize the Maine Angels stacked up so well against larger and more well-known angel groups. Such a ranking, she told me, will help raise the group’s profile in national circles and hopefully bring more exposure to its portfolio companies.

“I think being mentioned in a national venue like that that does a lot of hard data analysis is attractive both to the entrepreneurs we’re trying to seek out to improve the quality of our deal flow and attractive to our colleagues who might say, ‘Wow!'” Stone says.

Since its founding in 2003, Maine Angels has invested $12.6 million in 54 early-stage companies. Approximately 47 percent of those investments have been in Maine companies, including Ocean Renewable Power Co., the tidal energy startup in Portland; Pika Energy, the Westbrook-based company designing and building residential-scale wind turbines; and Cerahelix, the Orono-based company working to develop high-tech filtration coatings using DNA. Most of the rest of its portfolio companies are in Massachusetts. The group has also participated in 50 follow-on rounds for 28 of its portfolio companies.

So far this year the group has participated in 21 deals, with another ready to close in the coming weeks, Stone said. About half are follow-on investments.

Maine Angels has yet to experience an exit event with one of its portfolio companies — usually an experience that follows an IPO or acquisition and provides a return to investors — but Stone says they could be getting close.

This is not the Maine Angels’ first time in the national spotlight. In the 2013 Halo Report, an annual report on angel investing that is also derived from CB Insights data, placed Maine Angels as the 10th most active angel investment group in the country in 2012. That list was ranked by the number of deals completed in the last year.

(This article was updated on Aug. 22 to reflect some updated figures for Maine Angels’ total investment and number of follow-on rounds.)