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Age in place? Hardly. Retirees are on the hunt for better weather and lower costs of living.

An estimated 4.2 million retirees moved into a new home last year, according to a new study from Merrill Lynch and Age Wave. And almost two-thirds of retirees say they will move at least once in retirement. (One possible reason why: By age 61, a majority of people have crossed the "Freedom Threshold," researchers posit, meaning they are free to choose where they want to live rather than be tied to a specific place by work and family obligations.)

"The natural extension of that freedom is choice," said David Tyrie, head of retirement and personal wealth solutions for Bank of America Merrill Lynch. "One of the most popular questions is, should I stay or should I go?" Some drivers include empty nesting, divorce or health challenges, but the biggest is being close to family, he said.

Asked to grade their location, more than 3,600 retirees and soon-to-be retirees gave these spots top marks.

—By CNBC's Kelli B. Grant
Posted 25 Feb. 2015

Robert Daly | Getty Images