As we noted in our discussion of open market operations, in a limited reserves environment the FOMC can affect banks' balance sheets and the money supply. The following figures shows this process in detail.
Changes in Happy Bank's Balance Sheet

CNX_Econ3e_C28_014 (a) shows that Happy Bank starts with $460 million in assets, divided among reserves, bonds and loans, and $400 million in liabilities in the form of deposits, with a net worth of $60 million. When the central bank purchases $20 million in bonds from Happy Bank, the bond holdings of Happy Bank fall by $20 million and the bank’s reserves rise by $20 million, as CNX_Econ3e_C28_014 (b) shows. However, Happy Bank only wants to hold $40 million in reserves (the quantity of reserves with which it started in Figure 15.5) (a), so the bank decides to loan out the extra $20 million in reserves and its loans rise by $20 million, as CNX_Econ3e_C28_014 (c) shows.

CNX_Econ3e_C28_015 (a) shows the balance sheet of Happy Bank before the central bank sells bonds in the open market. When Happy Bank purchases $30 million in bonds, Happy Bank sends $30 million of its reserves to the central bank, but now holds an additional $30 million in bonds, as CNX_Econ3e_C28_015 (b) shows. However, Happy Bank wants to hold $40 million in reserves, as in CNX_Econ3e_C28_015 (a), so it will adjust down the quantity of its loans by $30 million, to bring its reserves back to the desired level, as CNX_Econ3e_C28_015 (c) shows.
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