货银 米什金 Chapter 9

5. If the bank suffers a deposit outflow of $50 million with a required reserve ratio on deposits of 10%, the deposit will lose $50 million of deposits and $50 million of reserves, and now its required reserves are 10% of $450 million ($45 million), but now it only has $25 million, which means we need $20 million more for reserves.

We have three ways to keep the bank from failing:

(1) Borrow $20 million from other banks or corporations,

(2) Borrow $20 million from the Fed,

(3) Call in or sell off $20 million loans.

6. The bank would rather have the balance sheet shown in this problem, because after it loses $50 million due to deposit outflow, the bank would still have excess reserves of $5 million: $50 million in reserves minus required reserves of $45 million (10% of the $450 million of deposits). Thus the bank doesn’t need to alter its balance sheet and would not take any costs as a result of the deposit outflow. By contrast, with the balance sheet in Problem 5, the bank will take costs when it raises the necessary reserves through the methods described in the text below.

In a word, Excess reserves are insurance against the costs associated with deposit outflows. The higher the costs associated with deposit outflow, the more excess reserves banks will want to hold.