 These developments have begun a reversal of the city's population decline between 1950 and 2000 during which it lost about one-quarter of its residents.The city eventually began experiencing a growth in its population in 2007, which has continued with gradual yearly increases to the present.The geographic center of Philadelphia is located approximately at 40° 0′ 34″ north latitude and 75° 8′ 0″ west longitude.