When you deposit $100.00 into your account, your bank can legally take at least $90.00 of that deposit and loan it out without telling you. Your bank account still says it has $100.00 in it, because your bank left IOU's, called bank credit, in its place. This means that when the $90.00 of your currency that your bank loaned out is deposited in another bank, that bank can loan out at least 90% of that deposit, or $81.00, back out again to yet another bank. This process repeats and repeats so that banks lend out an average of $1,000.00 for every $100.00 you deposit. This also means that if banks offer loans at 5% interest, they are collectively making $50.00 in gross profit for every $100.00 you deposit every year.