Though researchers say there are no interpretive conclusions to be made from a report issued this week about Maine’s populated offshore islands, there are indications that the islands as a group are succeeding in maintaining their status as viable year-round communities.

But if anything is to be taken from the report, produced by the Rockland-based Island Institute, it is that there needs to be more thorough collection of data from each individual island community to get a more accurate picture of how it is faring, researchers said.

Maine has 15 islands with year-round communities and only ferry or air service to connect them with the mainland. They are dotted along the coastline from off Portland in Casco Bay to far-flung Matinicus 15 miles out to sea and to the Cranberry Isles near Acadia National Park.

The Island Institute, founded in 1983 to help conserve and support Maine’s island communities, for years has been focused on how to help them remain affordable for working people and how to preserve the resources that make them special. How many people live on them, their age, what they do for work, how educated they are, how much money they earn and what they pay for housing are among the issues that can determine whether a year-round island community thrives or withers away.

That’s why the institute decided to find out what kind of official objective statistics were being kept about life on the islands.

According to Kathy Westra, the institute’s communications director, a lot of the information researchers came across was anecdotal and so was not included in the report. She said the information in the report is not intended to support any argument or theory about the islands’ viability.

“It would be a mistake to draw interpretive conclusions from the data,” Westra said Thursday. “What we were trying to do with this study was to find out what information was available and to present it in an objective way.”

Among the information provided by the data is that the average age of island residents is older than that of the Maine average of 39 years; island residents tend to be slightly more educated but earn less money than their mainland counterparts; and the overall population of the 15 islands rose 7 percent between 1990 and 2000.

Sarah Curran, an institute fellow on Peaks Island who co-wrote the report, said Thursday that the population indicator can be “tricky.” Information wasn’t consistently available for all the islands, she said, and population figures decreased on some, such as the Cranberry Isles, Matinicus and Frenchboro.

Before cars became the dominant mode of transportation, however, many Maine islands had higher populations than they do today. Curran acknowledged that with that precedent in mind, it is a positive sign to see overall growth.

“For island communities, the loss of population can be devastating,” she said.

Westra said that the report also shows that islanders are heavily dependent on lobster fishing and tourism for their incomes. If these industries suffered a downturn, she said, the economies of the island communities could be inordinately affected.

One main reason there has been inconsistent record keeping for many of the islands is because of the way it has been handled by government entities, the researchers said.

Some islands, such as Peaks, Great Diamond and Cliff, are part of Portland, and so many of their vital statistics get anonymously lumped in with those collected citywide. Others, such as Great Cranberry Island and Little Cranberry Island, are both part of the same municipality and don’t always differentiate between one island and another when keeping records.

In other cases, U.S. Census data can easily be distorted by the level of response in small communities, and sometimes the information just isn’t available, the researchers said. There especially is a lack of historical environmental data from the islands.

Going forward, the institute hopes to collect official data from the islands every two years in order to help create a better historical record of how island demographics change or stay the same.

“We’ll be looking at improving it next time around,” Westra said.

Other islands that were included in the report’s findings are Long and Great Chebeague, both in Casco Bay, and Monhegan, Islesboro, North Haven, Vinalhaven, Isle Au Haut and Swans islands. More information on the report is available online at www.islandinstitute.org.