A key demographic in Maine’s tourism industry is on the rise, and the group’s tendency to vacation toward the tail end of summer is boosting late-season revenue for many of the state’s hotels and restaurants.

The 55-and-older crowd has long been a dominant force in Maine tourism. According to the Maine Office of Tourism’s most recent annual report, 35 percent of overnight visitors to Maine in 2014 were at least 55 years old, and the mean age of all overnight visitors was 47.

Tourism analysts say that’s because the 55-and-older set is the fastest-growing segment of the U.S. population, leading to a change in monthly revenue patterns for businesses that rely on tourists.

For example, since the recession, restaurant sales in Maine have been higher in September than in June, the opposite of what they had been historically.

“Probably about six or seven years ago, June and September flipped,” said Greg Dugal, president and CEO of the Maine Restaurant Association. “The disparity between June and September has continued to grow over time.”

The two months – often referred to as the summer tourism season’s “shoulder months” – continue to bring in fewer tourism dollars than the prime months of July and August. Still, the amount of revenue for all four months combined increased by nearly 40 percent from 2005 to 2014.

Combined lodging and restaurant sales in Maine totaled $325.5 million in June 2014 and $339.3 million in September 2014, according to the Maine Office of Policy and Management. That’s a boost of 38 percent for June and 32 percent for September compared with a decade earlier. Sales revenue for the four-month period from June through September increased 39 percent during the same period to $1.59 billion in 2014.

Dugal, who also is executive director of the Maine Innkeepers Association, attributed some of the increase to recent growth in the number of hotel rooms, particularly in Portland. Rising demand for summer lodging seems to have easily absorbed the 600 new rooms that have come online in Portland in the past two years, he said.

“It usually takes a long time to absorb that many rooms,” Dugal said.

September is also a busy month for cruise ship visits to Portland, along with October. The Aurora was docked Monday at the International Gateway Terminal, depositing nearly 2,000 passengers into the city. They were among the 50,000 passengers expected to visit Portland in September and October.

According to Cruise Market Watch, an industry analyst firm, 48 percent of U.S. cruise ship passengers are 50 or older and 39 percent have annual household incomes from $100,000 to $200,000.

Overall growth in lodging and restaurant sales has changed the equation for some businesses that used to shut down right after Labor Day, giving them a strong incentive to remain open a few weeks longer. That especially holds true when the weather stays warm, which it has been doing more consistently in recent years.

“The demographic has changed. The weather patterns have changed to where it’s warmer,” Dugal said. “September has been absolutely beautiful the last few years.”

Rich Redmond, owner of The Pier at Old Orchard Beach, said warm weather and higher sales have prompted his seasonal business to remain open beyond the peak tourist season longer than it has in the past.

“For the last week of September, we’re getting a good flow of people here,” Redmond said Saturday. “We’re trying to stay open past Columbus Day.”

Staying open later in the season isn’t easy because of staffing challenges, he said. Many of The Pier’s bar, restaurant and retail workers have school or other jobs to tend to after the peak summer season ends.

It is a two-week process to shut everything down, Redmond said, likening The Pier to “a ship that never moves.” So he has been checking the weather report each day and trying to cobble together enough staff to keep things running.

“Last year, we were already closed by now,” he said.

Down the street at Kebek 3 Motel, owner Marc Bourassa continues to welcome new guests, primarily in French since his establishment serves a customer base that is mostly French Canadian.

Bourassa was concerned that he would see an increase in cancellations because of the unfavorable exchange rate between the Canadian loony and the U.S. dollar, but said only a few of his mostly elderly clientele opted not to come as a result of the added expense.

“There were more cancellations due to medical reasons than due to the exchange rate,” he said.

Bourassa, who runs the beachfront motel with his wife and family, said occupancy is up in September, driven by an increase in older visitors. For added staff, he has been using the federal J-1 cultural exchange visa program, because J-1 workers tend to be able to stay on longer than U.S. college students.

“What’s happened is that September has become stronger,” he said.

Seniors Jim and Sandy Sullivan, who live in Massachusetts, said they chose to vacation in southern Maine in September because the rates are cheaper and the streets and businesses aren’t as crowded. They don’t mind that things tend to be a little quiet late in the season.

“That’s the good part,” Jim Sullivan said.