New Keynesian economics emerged as the leading theoretical framework for understanding modern monetary policy during the 1990s, synthesizing classical insights with modern microfoundations. Unlike their old Keynesian predecessors, who relied on rigid price assumptions, new Keynesians built models where prices are sticky due to real-world frictions. This focus on nominal rigidities provides the primary justification for active central bank intervention, particularly during demand shocks. The school’s influence peaked in the early 2000s, guiding responses to the Global Financial Crisis and the subsequent era of low inflation. Today, the framework remains dominant in central bank think tanks and academic macroeconomics departments, despite facing fresh challenges from pandemic-era supply shocks and shifting inflation dynamics.
The Core Mechanics of Price Stickiness
At the heart of the new Keynesian model is the assumption that firms cannot freely adjust prices. This stickiness is not the result of government regulation, but rather stems from real costs associated with changing prices, known as menu costs. These costs might include the expense of printing new menus, updating websites, or simply the time spent by managers recalculating rates. Because these costs are small on an individual transaction basis, firms often find it optimal to adjust prices infrequently and in small increments. This infrequent adjustment creates the nominal rigidity that allows demand-side shocks to have real effects on output and employment in the short run, a cornerstone of the school’s policy relevance.
The Role of Calvo Pricing
To model this behavior mathematically, new Keynesians often utilize the Calvo pricing framework. In this structure, each firm sets its price optimally at the beginning of a period but faces a constant probability, theta, of being able to reset its price in any given period. A firm with a Calvo parameter of 0.25, for example, can change its price 25% of the time, meaning the average duration of a price spell is four periods. This "state-dependent" mechanism implies that the likelihood of a firm adjusting its price does not depend on how long it has been since the last change, but rather on the current state of the economy. This specific feature ensures that price dispersion—where some firms raise prices while others do not—exists simultaneously in the economy, which is crucial for the transmission of monetary policy.
Monetary Policy and the Phillips Curve
The presence of sticky prices directly links new Keynesian theory to the Phillips Curve, the inverse relationship between inflation and unemployment. Because firms are slow to raise prices, an increase in aggregate demand does not immediately lead to higher wages or production costs. Instead, output increases first, and inflation follows with a lag. This provides a clear theoretical justification for central banks to respond to demand shocks. By raising interest rates to cool demand, a central bank can prevent the economy from overheating and inflation from accelerating. The standard New Keynesian Phillips Curve is the primary tool used to analyze this trade-off, making it an essential instrument for forward-looking policy decisions.
