This paper quantifies the impact of monetary policy shocks on asset markets in the United States and gauges the usefulness of a shadow short rate as a measure of conventional and unconventional monetary policy shocks. Monetary policy surprises are found to have had a larger impact on asset markets since short term interest rates reached the zero lower bound. Our results indicate that much of the increased reaction is due to changes in the transmission of shocks and only partly due to larger monetary policy surprises.