The growth of Philadelphia's young-adult population in recent years has been hailed as one of the more positive developments in the city's recent history and a possible key to its future.Since 2006, when the city's population reached its lowest point in a century, no major city has experienced a larger increase in 20- to 34-year-olds than Philadelphia, as measured by the change in their percentage of each city's overall population.

This boom, however, appears to be as fragile as it is promising. Young adults -- members of the nation's vast millennial generation -- are drawn to the city by its vibrancy, diversity, culture, and nightlife. But many of them voice a familiar set of concerns about life in the city, bemoaning the dirty streets, the crime, and the perennially troubled school system. And they are contending with a local job market that many consider to be lacking in the kinds of opportunities that lead to careers.

In a Pew Charitable Trusts poll, half of the 20- to 34-year-olds questioned said they definitely or probably would not be living in Philadelphia five to 10 years from now, compared with about 3 in 10 for the rest of the city's adult population. The millennials cited job and career reasons, school and child-rearing concerns, and crime and public safety as the primary reasons for their potential departures. Using demographic data, focus groups, and polling results, Pew took a close look at Philadelphia's young adults, a group that has brought the city a renewed sense of vitality and hope and has enlivened its streets, day and night.