According to a number of news reports, NSA has been collecting 125 billion calls in just one month.
As you can see from the heat map, most of the calls originated from the middle east. So the number of calls that the NSA collected are
Pakistan: 12.76 Billion
Afghanistan: 21.98 Billion
India: 6.28 billion
Iraq: 7.8 billion
Saudi Arabia: 7.8 billion
United States: 3 Billion
Egypt: 1.9 Billion
Iran: 1.73 Billion
Jordan: 1.6 Billion
Germany: 361 Million
France: 70.2 Million
Spain: 61 Million
Italy: 46 Million
Netherlands: 1.8 Million
The rest of the world: Lots and Lots
Total: 124.8 billion.
They were able to capture so much data because phone call, email or chat will take the cheapest path, not the physically most direct path. Much of the world’s communication flow through US.
One intriguing thing I noticed is that how they were able to have enough computing power to process those immense data considering that the budget is only $20M per year. (Were they using EC2 for free?)
Reference
[1] http://cryptome.org/2013/10/nsa-125b-calls.htm
[2] http://cryptome.org/2013/10/nsa-prism-13-1021.pdf