The influx of new Philadelphians has been a source of pride and controversy in the city of brotherly love, but have you ever wondered where all these people are coming from? Here's a map that charts migration flows from county to county. In concrete terms, that means you can find out exactly how many people left Payne County, Oklahoma for Philly (that number is 51, in case you were dying to know.) You can also use the maps to find out where Philadelphians go after leaving the city, but that's somewhat less interesting (the map shows that most of them leave for the 'burbs.)
Here, for instance, is a map of where people leave Philly for:
Here is a map of counties that have lost more than 500 people to Philly in the Northeast:
The map is an excellent time suck, as you can hone in on any county in the country. You can also track how many people moved in and out of counties according to education level and income.
If you're really interested in getting down to the nitty-gritty details, the Census Bureau has also included data tables, so you can see exact numbers.
· Census Flows Mapper [Census.gov]