Expansionary monetary policy constitutes a transfer of purchasing power away from those who hold old money to whoever gets new money. This is known as the Cantillon Effect, after 18th Century economist Richard Cantillon who first proposed it. In the immediate term, as more dollars are created, each one translates to a smaller slice of all goods and services produced.
How we measure this phenomenon and its size depends how we define money. This is illustrated below.
Here’s GDP expressed in terms of the monetary base: