His Wall Street fortune was built using data as an investment beacon. He is rebuilding the 76ers with the same gusto for analytics. And on Thursday, Josh Harris made clear he has put the Philadelphia Police Athletic League through the private equity wringer.

In announcing his $3.5 million donation to the group serving boys and girls with sports and other after-school programs, Harris subjected the nonprofit to the same scrutiny that has earned him a fortune as cofounder of Apollo Global Management L.L.C.

Harris hired a consulting firm to interview people inside and outside the organization. He personally helped the group draft a detailed five-year plan that includes ways of measuring improvements in the well-being of children who use PAL's 18 centers.

He insisted on all of this and more over a year and a half, before handing over the largest gift in the 68-year-old group's history. The donation will be disbursed over the next five years, a major boost to an operating budget that relies on about $2.2 million in annual revenue, plus donated wages and salaries of police who staff the centers.

"We put them through Apollo-style [due] diligence," Harris told a packed crowd during a news conference at PAL's Harrowgate center at 851 E. Tioga St., in one of the city's poorest neighborhoods.

"They happily acceded," Harris added with a smile.

"This is huge," said Police Commissioner Charles H. Ramsey.

Harris, 50, is a graduate of the University of Pennsylvania's Wharton School. He grew up near Washington but has Philadelphia ties that run deeper than just the affection for his alma mater or the 1983 Sixers team that won the NBA championship.

"A city," Harris told the recreation center, full of cops, kids, and media members, "which I love."

His mother was born near Broad Street and Olney Avenue, and attended Temple University. His father, a native of Caldwell, N.J., graduated from Penn. Harris was raised in Chevy Chase, Md., but lots of family on his mother's side remain in Philadelphia.

PAL officials said that Harris approached them through advisers, and that the sides worked intensively to determine how much he might give and how it could best be put to use.

"What attracted him to PAL was the scale that PAL has," said Jeffrey B. Hendrey, chairman of the board. Each year, PAL centers serve 17,000 boys and girls ages 6 to 18.

Harris hired the Bridgespan Group to investigate programs across the country that could serve as models for how to enhance some of PAL's programming. It also dug around to understand the group's operations and objectives.

One dignitary who took the lectern Thursday looked at Harris, seated nearby, before it was his turn to speak and shared a recollection of that process.

"I spent two hours on the phone with the firm that you hired," said Susan Slawson, the city's deputy commissioner of recreation and programs. "They were serious."

Now a billionaire who lives in Manhattan with his wife, Marjorie, and five children, who range in age from 5 to 17, Harris' philanthropy is fueled by a desire to reach young people through programs that use sports.

The Harris Family Charitable Foundation, he said, was his way of trying to make a difference, given the enormous bounty of his own good fortune.

"All of us who have done well over our lives, we have the responsibility to give back," Harris said. "I myself grew up playing sports, and it lifted me, you know?"

mpanaritis@phillynews.com 215-854-2431 @Panaritism