For each dollar the bank has on deposit,
it can loan nine. This is because the US has a 10% reserve requirement.
http://en.wikipedia.org/wiki/Reserve_requirement
http://en.wikipedia.org/wiki/Fractional-reserve_banking
This 10% reserve requirement is one of the reasons why there is so much easy (deflated) money in our economy. It also helps to explain the size of the gap between rich and poor.
For comparison, Brazil has a 20% reserve requirement. This means for each dollar it has on deposit, a Brazilian bank is only allowed to loan four! This one of the reasons why Brazil's economy is so much sounder than ours.
Of course, there's a lot more to this, and I haven't connected the dots, but I'm not about to start a course on fractional reserve banking in this thread.