Looking for a big change in retirement? Here's the 2015 list of the 25 top U.S. cities for retirement. We sifted a lot of data covering housing and other costs of living, taxes, crime rates, weather and air quality, doctor availability and opportunities for an active lifestyle, including walking, bicycling volunteering. Also in the mix: economic data for those eying a 'working' retirement or simply a growing community. A fuller explanation can be found here. Cities are listed in alphabetical order.