Kolko explains the relevance of the Census data release: "[the] new data tell us whether key demographic groups – like millennials (20-34 year olds), boomers (50-69 year olds), and young kids (0-4 year-olds) – might be bucking the broader trend of more suburban counties growing faster than the most urban counties."
Here's how Kolko describes the narrative revealed by the data: "millennial population growth in 2012-2013 in big, dense cities was outpaced by big-city suburbs and lower-density cities and even by lower-density suburbs and smaller cities. Boomer growth in big, dense cities also fell just short of growth in the big-city suburbs and lower-density cities. But the population of kids under the age of 5 grew fastest in big, dense cities."
Plenty more detail is offered in the article's breakdown by age group, but here are the headlines: "Millennials Not Flocking to Big Cities," "Boomers Getting More Urban," and "The Big-City Baby Boom."