From 2015 to 2040, Norwich is projected to see the state's seventh-highest percent increase in population, and New London and Lyme also are looking at population growth, according to new projections from the Connecticut State Data Center.

But the outlook isn't as rosy for other southeastern Connecticut towns. The Data Center predicts declining population in most of the area's towns, with only the 65-plus demographic growing.

"The new projections show that multiple towns are approaching a demographic shift due to an aging population, a near net zero overall migration rate, and a relatively low, but stable birth rate," stated a news release from the Data Center.

The projections include the estimated population in 2015, 2020, 2025, 2030, 2035 and 2040 for every city and town in the state. For each town, projections for each year are broken into 18 age groups, and each age group is divided into male and female.

The 2015 numbers are projections because the census only takes place in years that are multiples of 10. The main inputs the Data Center used, Director Michael Howser said, are birth and mortality data from the Connecticut Department of Public Health and migration data from the U.S. Census Bureau.

Howser said the Data Center has spent about two and a half years putting together the projections, with two to four people working on the project at a given time. The Data Center has been putting together projections since the 1990s, and the last set came out in 2012.

In the past five years, growth in Connecticut has been slower than the Data Center projected in 2012, Howser said.

"Generally speaking, Connecticut has one of the lowest birth rates in the country, and our surrounding states have some of the lowest birth rates, as well," he said.

But for Norwich, the Data Center projected population growth from 2015 to 2040 across all age groups, for total growth of 28 percent. Only six municipalities have higher figures: Windham, East Windsor, Avon, West Haven, Ellington and Oxford.

Asked about possible reasons for the positive outlook, Norwich Mayor Deberey Hinchey cited a "fair amount of affordable housing stock," access to routes 395 and 2, and two new breweries downtown, which she noted can attract younger people.

"I think it's a combination of economic and sort of citywide development that we've been working on for a number of years," she said.

In New London, Mayor Michael Passero pointed to new development agreements for housing projects, such as Shipway 221 and Parcel J, as a factor of the city's appeal. He asserted that New London can appeal to millennials who "want to live, work and play in the same place," but also to senior citizens.

"A lot of the so-called empty nesters are tired of living out in the 'burbs, and tired of the manicured lawn and all that crap," he said. "They just want to retire to an apartment or a condo in a walkable city, so we're hoping to really capitalize on both age groups, at either end of the spectrum."

On the younger end, he noted that Electric Boat is creating engineering and construction jobs that will draw in young talent.

Sam Alexander, a planner for the Southeastern Connecticut Council of Governments, also pointed to this as a reason why Groton might see growth despite projections of a 3.2 percent decrease in population from 2015 to 2040.

SECCOG is using the population projections for a study on housing needs in the region through 2030, which it is completing for the Southeastern Connecticut Housing Alliance.

Alexander pointed out that even if towns are losing population and the average age is getting higher, "they might not necessarily be losing households, because those older people are more likely to live alone or live in a two-person household than a younger person would."

In East Lyme, Ledyard, Montville, North Stonington, Preston, Salem, Stonington and Waterford, the only age group expected to grow is 65 and older.

The projected 16.8 percent decrease in Stonington's population from 2015 to 2040 is especially striking, considering population estimates the U.S. Census Bureau released in May indicated that Stonington saw the largest population increase in the state between 2015 and 2016.

In East Lyme, North Stonington, Preston, Stonington and Waterford, the largest age group now is 35-54, but 65+ is projected to overtake it by 2040. In Ledyard, Montville and Salem, 35-54 is expected to remain the largest age group, despite a projected decline in numbers.

The forecast looks better for Lyme, with the population rising from 2,499 in 2015 to 2,742 in 2040. Using both past U.S. Census Bureau figures and future analysis, the Data Center lays out line graphs for each town from 1970 to 2040, and at no point on Lyme's chart does the population decrease.

e.moser@theday.com