What is the liquidity effect and how to model it are two frequently debated questions among monetary economists, that have received extensive attention in recent years. Evidence based on a structural VAR shows that when the Fed surprises financial markets by suddenly decreasing the rate of money growth through an open market sale, the nominal interest rate rises on impact, in company with a drop in aggregate employment and output. Prices, however, are affected gradually. This is the so called liquidity effect. Therefore, any plausible model of monetary policy should account for this behavior. Several competing monetary models currently exist with each employing a different transmission mechanism of monetary policy.
Two of the most popular transmission mechanisms of monetary shocks in the recent literature are price stickiness and financial market frictions. In a sticky price environment, such as Kydland (1989) and Christiano (1997), monopolistically competitive producers are unable to immediately adjust prices in response to a monetary shock. Those models attempt to explain the responses of aggregate output and prices, but fail to generate observed variability in the nominal interest rates following a monetary policy shock. On the other hand, in a limited participation environment, for instance Lucas (1990) and Fuerst (1992), money plays a role in the economy due to its asymmetric distribution among economic agents. Those models, in contrast to sticky price models, give rise to a small liquidity effect, but have difficulty in producing the appropriate effects on output and prices. Moreover, the liquidity effect in those models exhibits no persistence and only exists in the impact period of the policy action. To reproduce the desired liquidity effect, several remedies have been proposed, one of which (Christiano, Eichenbaum and Evans (CEE) 1997) suggests that embedding labor market frictions into either type of model might help generate the liquidity effect and prolong the impact of monetary shocks.