The Phillips Curve Explained: Inflation vs Unemployment in Economics

Rational expectations theory assumes that individuals are highly intelligent and use all available information (not just historical data) to form expectations. People consider current economic conditions, government policies, and all relevant data sources when forming expectations. Under rational expectations, the short-run Phillips curve is vertical. When the government announces policy changes, people immediately adjust their expectations accordingly. If the government promises to reduce inflation, people immediately adjust their wage demands and price expectations, causing the economy to move directly to the new equilibrium without the gradual adjustment process seen in adaptive expectations. Under rational expectations, both the short-run and long-run Phillips curves are vertical. This is because people anticipate policy changes immediately and adjust their behavior accordingly. The economy moves directly to the natural rate of unemployment regardless of inflation policy, meaning there is no trade-off between inflation and unemployment even in the short run. The key differences between expectations theories are: adaptive expectations show a trade-off in the short run but not in the long run, while rational expectations show no trade-off in either the short run or long run. Both theories agree that in the long run, the economy returns to the natural rate of unemployment with no trade-off between inflation and unemployment.

Changes in expected inflation rate shift the Short-Run Phillips Curve. If people expect higher inflation, they will demand higher wages and prices will rise more quickly, causing the Phillips Curve to shift upward (to the right). If people expect lower inflation, the curve shifts downward (to the left). This occurs because expectations affect economic behavior: if people expect prices to rise, they will spend more now, which causes prices to rise faster than expected. This creates a self-fulfilling prophecy where expectations of inflation cause inflation to occur.

Changes in inflation expectations cause systematic shifts in the short-run Phillips curve. When inflation expectations rise, the curve shifts right, increasing both unemployment and inflation. When expectations fall, the curve shifts left, reducing both. Three types of expectations exist: static (expecting current inflation equals last year's actual), adaptive (learning from past forecast errors), and rational (using all available information without systematic errors). Static and adaptive expectations are backward-looking, creating inflation inertia where past inflation perpetuates future inflation through wage and price setting behavior.

When households and firms observe higher actual inflation, they incorporate these observations into their inflation expectations. This change in expectations causes the short-run Phillips Curve to shift upward. For any given unemployment rate, higher expected inflation means higher actual inflation will occur. This mechanism explains why attempts to reduce unemployment below the natural rate through expansionary policy eventually fail, as inflation expectations adjust and push the economy back toward equilibrium.

The new Keynesian Phillips curve incorporates rational expectations of future inflation, derived from Rotemberg (1995) and used in modern DSGE models. It distinguishes between short-run tradeoffs and long-run equilibrium. The NAIRU theory distinguishes between short-run and long-run Phillips curves: short-run allows temporary unemployment reductions through expansionary policy, but this raises inflation expectations, shifting the curve outward. The rational expectations theory suggests the short-run period is negligible, making any attempt to reduce unemployment below NAIRU immediately fail as expectations adjust. This framework provides sophisticated tools for analyzing monetary policy and inflation dynamics.

In the 1970s, oil shocks from the Yom Kippur War and Iranian Revolution caused stagflation (inflation and recession). Inflation expectations got out of control because central banks were behind the curve. Paul Volcker, appointed by Carter in 1979, raised interest rates to 20% to fight inflation, causing a severe recession in 1981-82 but successfully breaking inflation expectations.

The 1970s experienced stagflation—economic stagnation combined with high inflation—challenging the traditional Phillips Curve relationship. The US printed money to fund the Vietnam War without raising taxes, causing money supply growth. When oil prices spiked in 1974, central banks responded by increasing money supply to combat recession, further fueling inflation. The 'Klunker Round' of 1974, where public sector unions demanded 14% wage increases, accelerated inflation. Paul Volcker implemented aggressive monetary policy by raising interest rates to 20%, breaking the wage-price spiral and establishing central bank independence. However, fiscal dominance now occurs when fiscal policy controls monetary policy, undermining central bank independence and creating conditions favorable for inflation.

In 1979-1981, Federal Reserve Chairman Paul Volcker implemented aggressive monetary tightening, raising interest rates to 20% to combat stagflation. This extreme measure caused severe economic contraction, including a 37% stock market crash in 1981. However, it successfully broke the stagflation cycle, leading to the prosperous 1980s decade. The episode demonstrates that resolving stagflation requires accepting significant short-term economic pain.

Stagflation (stagnation plus inflation) characterized the 1970s, presenting a fundamental policy challenge: raising rates to combat inflation worsened stagnation, while lowering rates worsened inflation. This regime of persistent volatility featured frequent recession-recovery cycles and dramatic inflation fluctuations. The experience demonstrated that economies could enter a regime of persistent instability requiring fundamental policy changes. The 1970s oil shocks created structural changes that made stagflation a persistent feature until the Volcker shock in the early 1980s.

Economic systems evolve to address contemporary problems: free-market capitalism failed during the Great Depression, leading to modified capitalism (Keynesianism), which then failed during stagflation, giving way to neoliberalism in the 1980s. The 1970s US economy faced stagflation—simultaneous high inflation and stagnation—caused by Vietnam War spending, the 1971 Nixon shock, and the 1973 oil crisis. Paul Volcker, appointed in 1979, implemented unprecedented monetary policy, raising interest rates from 5% to 21.5% by 1982. This caused severe recession and 10% unemployment but succeeded in reducing inflation from 20% to 2% by 1983. This experience created generational differences in economic risk perception: those who lived through the crisis developed deep fear of debt, while younger generations who entered the workforce after the crisis tend to view debt more casually.

The Phillips curve describes the inverse relationship between unemployment and inflation. After the Great Financial Crisis, when unemployment fell to historically low levels during the Obama and Trump administrations, inflation did not rise as expected. This flattening meant traditional monetary policy tools became ineffective. The Fed responded by shifting from attempting to force inflation through money printing to instead managing inflation expectations, fundamentally changing how monetary policy operates in the modern economy.

The new monetary orthodoxy faces the zero lower bound problem - when interest rates approach zero, central banks cannot lower them further to stimulate the economy. Modern research on the Phillips Curve shows that when inflation expectations are anchored, inflation remains stable even with significant unemployment. This suggests inflation is more stable than previously thought. The speaker presents the view that inflation is a phenomenon of expectations, and economists have little to say about expectations, suggesting monetary policy involves more psychology than traditional models capture.

The Phillips curve, which historically linked unemployment to inflation, has flattened since the Great Financial Crisis. This means wage growth no longer drives inflation as it did before. The top 20% of households consume 75-80% of goods and services, while the bottom 80% contribute only 25-30%. This concentration means inflationary pressure comes from wealthy consumers, not working-class wage growth.

The Phillips curve relationship between unemployment and inflation broke down during the Obama and Trump administrations, where historically low unemployment coexisted with persistently low inflation. This 'flattening' represented a fundamental breakdown of traditional monetary policy frameworks. The Fed realized that even with full employment, inflation did not materialize as expected. This crisis forced the Fed to develop new strategies, including the 'opportunistic reflation' approach, to find alternative sources of inflationary pressure beyond traditional employment-driven mechanisms.

The Phillips Curve, which traditionally showed an inverse relationship between unemployment and inflation, has flattened in recent decades. This means that reducing unemployment no longer reliably increases inflation, challenging traditional economic models.