Since the end of World War II, a main question about U.S. Census figures for Twin Cities suburbs was not whether they added residents, but how big those population increases were.

Not this time.

A record 26 suburbs in the seven-county metro area lost population, according to recently released data from the 2010 census. That's twice as many showing declines as in the previous census.

Many ring the borders of Minneapolis and St. Paul, reflecting the same rippling effects of population loss a generation ago in city neighborhoods. But losses also were reported farther out in wealthy suburbs that ring Lake Minnetonka, wide-open areas of western Hennepin County and old blue-collar cities to the north, east and south.

Most of those cities were still gaining population 10 years ago. Wayzata, for example, grew by 8 percent in the 2000 census but dropped by more than 10 percent in the 2010 count.

Mayor Ken Willcox said he was mystified by the decline, which amounted to 425 people in the city of 3,688 residents. He theorized it could be linked to a larger population of snowbirds who were in Arizona or Florida when the census forms came, or to the departure of young residents who have grown up and left.

That makes sense to State Demographer Tom Gillaspy. Wayzata and suburbs like it, he said, are getting old, part of a demographic wave that hit first-ring suburbs in 2000 and now is creeping further into suburbia.

The seven-county metro area grew by 7.85 percent to 2.85 million people, fueled by suburban growth elsewhere in the region.

But by 2010, declines moved into Anoka, Arden Hills, Coon Rapids, Corcoran, Dayton, Deephaven, Falcon Heights, Mendota Heights, Minnetonka, Mounds View, New Brighton, Orono, Roseville, Shoreview, Shorewood, Spring Lake Park and Vadnais Heights. Eight other suburbs lost people in the 1990s, as well: Bloomington, Crystal, Fridley, Mound, New Hope, Newport, Robbinsdale and White Bear Lake.

Gillaspy said suburbs have a life cycle: a building and population boom at the start, followed by a few years of stability, and then declining family and household sizes.

"It gets down to the point where the process stalls out and they reach their minimum point, when families are really getting old," Gillaspy said. "The closer in the suburb is, the nearer it is to that transition point."

Bloomington, the metro area's most populous suburb, has lost population for two census cycles, even though it added 537 housing units in the past 10 years. The city now has 82,893 residents.

Glen Markegard, the city's acting planning manager, believes the loss may be linked to higher vacancy rates in city housing and shrinking household sizes as kids grow up and leave home.

"There's kind of a natural progression in household sizes," Markegard said. "Look at Minneapolis and St. Paul -- they went down, down, down and then in 2000 they went up. As homes turn over, you sort of hit bottom and then turn over to younger families."

Turning the trend around

Golden Valley, with 20,371 people, lost population in the last census and gained slightly in 2010. City Planner Joe Hogeboom said the city has just started talking about building more senior housing. He thinks his city is growing partly because of its commuting proximity to downtown Minneapolis and corporate campuses like those of General Mills and Honeywell. The city's large lots and bigger homes also attract growing families, he said.

Minnetonka charted a 3 percent drop in the 2010 census, after gaining more than 6 percent in 2000. Community Development Director Julie Wischnack said the city of just under 50,000 people is "no longer the growth suburb it once was.

"There are not a lot of housing starts now, and household size has diminished," she said. "We have a fair number of people who don't live here for the majority of the year. ... It's a symptom of people making transitions in their lives."

Minnetonka officials are talking about those demographic shifts and, like urban neighborhoods of a generation ago, are trying to develop what Wischnack described as "an action plan to make sure the community maintains its viability."

A study by the nonprofit Urban Land Institute-Minnesota targeted issues in Minnetonka, including that the city needs to actively address issues with aging housing stock, Wischnack said.

Three-quarters of the city's houses are more than 30 years old and need expensive updates like replacement of roofs, windows and furnaces. Older residents on restricted incomes may be reluctant to spend for such improvements.

Minnetonka is considering setting up revolving loan programs to help residents rehabilitate homes and help buyers with down payments or closing costs on a local home. Wischnack said the program would be aimed mainly at middle-class people looking to buy a house worth less than $300,000.

Forward-thinking suburbs should be thinking about their housing stock, but it's about more than that, said Libby Starling, research manager at the Metropolitan Council. "Simply having the houses there doesn't mean people want to live there," Starling said. "It's about schools, parks, proximity to where jobs are and other amenities."

Starling said some communities are growing partly because they are attracting minority homeowners, who tend to be younger than the overall population. The list includes Brooklyn Park, Brooklyn Center, Richfield, St. Louis Park, Maplewood, Oakdale, Burnsville and Apple Valley.

Richfield, a classic post-World War II suburb, boomed in the 1950s as families grew up and out of Minneapolis and returning GIs started families. The city saw its population fall in the 2000 census, but it grew by more than 2 percent in the 2010 census.

Community Development Director John Stark said the city is seeing the payoff for a strategy developed in the mid-1990s: build senior developments to keep folks in the city and free up homes for young families.

"Our housing starts stopped around 1968," Stark said. "If you just sit back and let things happen on their own, you're going to keep losing population. You have to have a strategy to affect where your population is going."

Mary Jane Smetanka • 612-673-7380