PORTLAND — A group of Portland business owners and the Maine Center for Economic Policy unveiled a study this morning that says spending money with local merchants generates more economic activity – and more local jobs – than shopping at national chains.

The study found that every $100 spent at locally owned businesses contributes an additional $58 to the local economy compared to $33 when the same amount is spent at national chains.

“The data shows pretty clearly that a slight change in consumer behavior can have a dramatic impact on the economy,” said Garrett Martin, executive director of the Maine Center for Economic Policy. “That does yield significant benefits for the economy.”

Martin said a shift of 10 percent in consumer spending in Cumberland County from national chains to locally owned businesses would result in $127 million in extra economic activity and support 874 new jobs.

The news conference announcing the study was held in the foyer of Longfellow Books, a locally owned bookstore in Monument Square. Owner Chris Bowe praised the efforts of the Portland Independent Business & Community Alliance, the nonprofit organization behind Portland’s “buy local” campaign.

Melissa Rivera, owner of Lalo Boutique on Congress Street, said her shop specializes in products made in Maine and many of her customers shop there for that reason. She said the city merchants’ “buy local” efforts have paid off in customer traffic.

“If they’re looking for me, then they know what I’m specializing in,” she said.