We hear a lot these days about the need to make communities smart and sustainable. But there's another aspect of our communities that is getting more and more attention, not only from forward-looking public officials but also in university studies and international conferences: preparing communities to be friendly for the unprecedented aging of their populations.

It's not hard to see why more communities are recognizing the need to be age-friendly. According to data from the Census Bureau and AARP, one in three Americans is 50 or older now, and by 2030 one in five will be 65 or older. Long before that, however, the 76.4 million baby boomers will be making their needs known as the generational gap widens: The 50-plus contingent will grow over the next decade by 19 million, compared to only 6 million for the 18-49 population.

This cohort of aging Americans is characterized by longer life expectancies, more energetic lifestyles and greater economic power than previous older generations enjoyed. As they look at their communities, age-friendliness -- the state of policy-making and planning for everything from health care and housing to economic development and transportation -- is going to become even more important to them. "Many thought leaders now believe that the communities that fare best in the 21st century will be those that both tackle the challenges and embrace the positive possibilities that an aging population creates," as Grantmakers in Aging put it in a 2013 study.