Read this and learn
http://pages.uoregon.edu/jlindo/ECN1B_files/ECN1B_How_the_money_multiplier_works.pdf|This is the simplest explanation of the money multiplier I've seen. ]
This is not a theory, it is a daily reality in the banking world. Now if you understand it, think about what happens to the money that is flowing through society on a daily, weekly, monthly basis. It is multiplied everytime it is spent and deposited.
This is why unemployment benefits work faster than tax cuts. People on unemployment deposit their checks, then spend it immediately, it goes into someone else's account and the money has multiplied.
This why GWB gave his "stimulus" checks to people to boost the economy. Remember that?