The number of Connecticut residents, particularly college graduates, moving out of the state has economists making ominous predictions for the state’s future.

Nearly 17,000 more people moved out of Connecticut than moved in between 2005 and 2006, according to recent U.S. Census estimates. Though Connecticut’s population actually increased slightly during this period, this growth was made possible primarily by an influx of about 14,300 immigrants from outside the country. Economists say the large number of working-age people moving out of Connecticut could negatively impact the state’s long-term economic health.

The out-migration, coupled with a declining share of college graduates in Connecticut’s workforce, is leaving the economy struggling to keep up, Connecticut Center for Economic Analysis Director Fred Carstensen said.

“In a competitive sense, we are falling behind other states,” he said. “Connecticut is clearly losing its competitive edge.”

Connecticut’s population of 3.5 million grew by 4,108 in the year that ended June 30, according to Census estimates based on administrative records such as birth and death records and IRS reports. The annual population increase numbers were in the mid-20,000 range at the beginning of the decade, but have continuously declined since then.

The Census Bureau does not break down its year-to-year data into age demographics, but economists said the two groups contributing most to the net out-migration were those ages 25 to 34 and those older than 55.

Economists identified a lack of affordable housing as a key reason for the slowdown in population growth. About one in every five Connecticut households is estimated to be in need of affordable housing, said Don Klepper-Smith, an economist based in New Haven. The category applies to households that earn less than 80 percent of the area’s median income but spend more than 30 percent of their budgets on housing.

Along with the affordable housing shortage, relatively stagnant job growth has encouraged working-age adults to move out of Connecticut, said Jeff Blodgett, vice president of research for the Connecticut Economic Resource Center.

“The two present a one-two punch for young folks beginning careers and starting families,” Blodgett said. “They’re forced to migrate to other parts of the country.”

Klepper-Smith said Connecticut’s high cost of doing business — 20 to 25 percent above national averages — has hampered job growth. He noted that the cost of doing business correlates with the cost of housing.

The resulting demographic shifts are depleting Connecticut’s working-age population, among them Yalies.

“Connecticut is one of the largest exporters of 25 to 34 age workers,” Klepper-Smith said. “When we take a look at Yale, we’re talking about you being our future workforce.”

The Census Bureau could not track the destinations of those leaving Connecticut between 2005 and 2006, but based on migration flow data from the 2000 census, the largest outflows of people from Connecticut are most likely directed to Florida, New York and Massachusetts, Census Bureau spokesman Robert Bernstein said.

On the bright side, New Haven appears to be an exception to some of the negative economic trends causing the out-migration, Carstensen said. Yale’s leadership has helped bring in new firms to the city, he said, giving it a more solid employment base than other parts of the state.

Out-migration is not limited to Connecticut — much of the Northeast is experiencing a similar population trend. Blodgett said states in the region should make a greater effort to work jointly on common issues, such as job creation and affordable housing.

“Until states in this part of the country start thinking and acting regionally, these issues are not going to go away,” he said.

Carstensen said if current trends hold, Connecticut’s population is projected to start declining shortly after 2020.