Philadelphia in 2016 is younger, more diverse, and in the midst of a historic, decadelong population upswing - a city undergoing dramatic change after decades of decline.

But some of the city's most enduring problems - poverty, low educational attainment, and unemployment - remain frustratingly unsolved, according to the Pew Charitable Trust's State of the City report, released Thursday.

The report described Philadelphia as a city transformed - but one that must use its encouraging growth as a stepping-stone.

"Philadelphia has been transformed by demographic trends that have produced growing populations across much of urban America," the report said. "The question is whether those trends are forming a foundation for real progress on the city's most persistent challenges."

Philadelphia's population grew by 5,880 people to 1,567,442 between 2014 and 2015. Since 2006, the city has added more than 78,000 residents - and as a result, its makeup is increasingly diverse.

In 1990, just 100,000 Philadelphia residents were foreign-born. That number has doubled, with immigrants arriving from Asia, Latin America, and the Caribbean, according to the report. And now, more than 23 percent of city residents identify as belonging to a race other than African American or non-Hispanic white - up from 9 percent two decades ago.

"You see a really quite striking change," said Larry Eichel, who directs the trust's Philadelphia research.

The city's population is also skewing younger, with a median age of 33.8, nearly four years younger than the national median age.

According to the report, it's the influx of young adults - the millennial generation - that has lowered the city's median age, even as the number of children in Philadelphia declined.

"We're a country that's been getting older," Eichel said, "and a city that's been getting younger."

Nick Marzano, president of Young Involved Philadelphia, said the city is in a unique position for real change.

His organization aims to help young Philadelphians engage civically - to have a hand in fixing problems, like the struggling schools system, that might otherwise begin to drive them out.

"As difficult and as impossible as [those problems] seem," he said, "if there's ever going to be a moment to tackle them, it's during a moment of growth."

The report called poverty "arguably Philadelphia's most daunting and intractable problem." The city's 26 percent poverty rate has declined slightly in the last several years, but remains the highest among the nation's 10 largest cities.

And the city's 7 percent unemployment rate - the lowest in eight years - is still 1.7 percentage points higher than the national rate. Jobs in Philadelphia are at their highest since 2002 - but job growth still lags behind national figures.

"There are continuing major issues that the city has," Eichel said. "They don't seem to be going away."

Mayor Kenney said in a statement Thursday that the report dovetails with his own plan to invest in prekindergarten programs, schools, and other community services, adding that his proposed soda tax is the "fairest choice" to increase funding for those investments.

awhelan@philly.com

215-854-2961 @aubreyjwhelan