Aggregate demand becomes upward sloping when the economy is stuck at the zero lower bound.  Thus, the economy may respond very differently to real shocks.  A positive technology shock which shifts aggregate supply downward can cause a large contraction in output.  However, these differential responses to shocks emerge when the central bank follows a standard Taylor rule (TR) subject to the zero lower bound.  This rule implies that the central bank stops responding to the state of the economy at the zero lower bound.  This assumption is inconsistent with the recent behavior by monetary policymakers.  The responses to shocks may not be so different if the central bank follows a history-dependent (HD) rule, which continues to respond the economy using expectations about future policy.