A change in the composition of the money supply can change the size of the money supply. For example, suppose M1  $1,000 billion, where the breakdown is $300 billion currency outside banks and $700 billion in checkable deposits. Now suppose the $300 billion in currency is put into a checking account in a bank. Initially, this changes the composition of the money supply but not its size. M1 is still $1,000 billion but now includes $0 in currency and

$1,000 billion in checkable deposits. Later, when the banks have had time to create new loans (checkable deposits) with the new reserves provided by the $300 billion deposit, the money supply expands.