Why does the Fed have imperfect control over the money supply over short periods?

Question

Quizplus · Accepted Answer

The Fed has imperfect control over the money supply over short periods because of unpredictable changes in public desire to hold cash and banks' desires to hold reserves. These factors can cause fluctuations in the amount of reserves in the banking system, which can affect the effectiveness of the Fed's attempts to control the money supply through open market operations. The other answer choices are not the primary reasons for this imperfect control.

Why Does the Fed Have Imperfect Control Over the Money