PORTLAND – Working waterfronts contribute more to the Maine economy than housing, according to a new report paid for by a coastal industry group.

The study found that the gap in economic impact between the state’s working waterfronts and coastal housing was at least $15 million in 2001 – and could be as much as $168 million annually.

The report was commissioned by Maine’s Working Waterfront Coalition, a group composed of more than 95 industry associations, nonprofit agencies, state agencies and individuals. The group is seeking changes in the state’s tax system that would reduce property taxes for waterfront businesses.

The report was written by former State Economist Charles Colgan, who is now a professor at the University of Southern Maine’s Muskie School.

“The evidence suggests that, while coastal real estate development does make a significant contribution to the Maine economy, those activities associated with working waterfronts make larger and more long-lasting contributions,” Colgan wrote in the report.

Ralph Townsend, an economics professor at the University of Maine, cautioned against placing too much weight on the report’s findings.

“They’re politically useful for the groups that generate them, but I don’t think they inform the debate very much,” Townsend said.

There is no dispute that the state’s coastline is becoming increasingly residential, especially in southern Maine. Two years ago, about 80 percent of 25 Maine communities surveyed said that shifting ownership of coastal property was an immediate or long-term threat to their fishing industries.

Jim Wilson, an economist and marine science professor at the University of Maine, said it would be difficult to measure the spinoff benefits of commercial and residential properties.

“It’s probably true that a mix is better than all residential, and a mix is better than all commercial,” Wilson added. “An awful lot of the summer people appreciate the Maine coast because of the mix it provides.”

Colgan concurred with that assessment.

“Neither all residential or all working waterfront is desirable,” he said. “Towns, in their planning, they need to be able to accommodate both.”

But commercial waterfronts have been undervalued, Colgan added, partly because housing tends to generate more property tax revenue.