If I remember from my economics classes correctly, a bank has to have around 10% of its assets liquid. Meaning if you have $100,000 dollars in the bank, they ne

If I remember from my economics classes correctly, a bank has to have around 10% of its assets liquid. Meaning if you have $100,000 dollars in the bank, they need to have $10,000 in cash on hand. Of course, the 10% is all assets, not just yours, so 100 customers have a total of 1 million dollars, the bank needs $100,000 on hand for withdrawals. That is just a broad overview that I remember from college. The numbers probably are wrong (10% is a nice round number) and I don't know how that works with a bank with 1000's of branches across the country. Of course I could be completely wrong, since I didn't really care about economics at the time.