The level of commercial bank reserves is determined by the size of the Fed’s balance sheet, and the proportion of reserves that end up in the Fed accounts of banks. When the Fed purchases securities or makes loans, it creates reserves out of thin air to fund them. A $100 purchase of Treasury securities results in the creation of $100 in reserves. A $100 FX Swap loan also creates $100 in reserves. Reserves can only be created or destroyed by …