So there is the slack, and you’ll wonder

How many developers are there in Philadelphia?

According to the 2014 census, you have approximately 1.5 million people in Philadelphia County, and 12.8 Million in Pennsylvania [1].

In the factfinder [2] for Philadelphia County, look at the Computer and mathematical occupation 12,210 +/- 846.

Right now we have 1338 in the Phillydev slack, so there are few more to join up.

[1] [2]