1. The Phillips Curve

2. Intro to Phillips Curve
There is a short-run trade-off between unemployment and inflation
Lower unemployment leads to higher inflation
Higher unemployment leads to lower inflation
This is inverse relationship is represented by the Phillips Curve!

3. Short Run Phillips Curve

4. Short-Run Phillips Curve
Demand shocks result in movement along SRPC
When AD increases along SRAS, unemployment rate ↓ and inflation rate ↑
When AD decreases along SRAS, unemployment rate ↑ and inflation rate ↓
Supply shocks result in shift of SRPC
When SRAS increases along AD, both unemployment and inflation rates ↓ (downward shift)
When SRAS decreases along AD, both unemployment and inflation rates ↑(upward shift)
SRPC can extend below the horizontal axis (in times of deflation)

5. Inflation Expectations
Expected rate of inflation: rate of inflation employers and workers expect in the near future
Affect short-run trade-off between unemployment and inflation
Matters because no one wants to lose purchasing power due to future inflation
An increase in expected inflation shifts SRPC upward
Relationship between changes in expected inflation and actual is one-to-one (will rise by the same amount)
Workers care about future inflation. If inflation is expected to be high in coming months, wage contracts should reflect that expectation and nominal wages will be increased. In fact, both workers and employers will factor expected inflation into all wage and price contracts because nobody wants to lose purchasing power due to future inflation.
For these reasons, an increase in expected inflation shifts the short run Phillips curve upward: the actual rate of inflation at any given unemployment rate is higher when the expected inflation rate is higher. In fact, macroeconomists believe that the relationship between changes in expected inflation and changes in actual inflation is one-to one. That is, when the expected inflation rate increase, the actual inflation rate at any given unemployment rate will increase by the same amount.
Why?
Suppose inflation has been near zero for years, but gradually people begin to expect inflation of 3%. Nominal wages and other contracts begin to reflect a future increase of 3%. As these wages and other resource prices rise by 3%, actual inflation begins to rise from about zero to 3%. So inflation expectations translate into actual inflation rates.
So, higher inflation expectations shift the SRPC upward. At any level of unemployment, inflation will be that much higher. Of course, this woks in reverse as well. Lower inflation expectations shift SRPC downward.

6. Long-Run Phillips Curve
Most macroeconomists believe there is no long-run trade-off between lower unemployment rates and higher inflation rates.
It is not possible to achieve lower unemployment in the long run by accepting higher inflation.
Let’s see why!

7. The efforts to decrease unemployment will increase the actual inflation rate. Over time, the public will come to expect a higher inflation rate. This increase in inflationary expectations will shift the SRPC upward. As a result, a persistent attempt to trade off lower unemployment for higher inflation leads to accelerating inflation over time.
To avoid accelerating inflation over time, the unemployment rate must be high enough that the actual rate of inflation matches the expected rate of inflation.

8. Natural Rate of Unemployment Revisited
Non-accelerating inflation rate of unemployment: represents the unemployment rate at which inflation does not change over time (NAIRU)
Keeping unemployment below NAIRU leads to ever-accelerating inflation—cannot be maintained
NAIRU is another name for natural rate
Level of unemployment needed in order to avoid accelerating inflation
Recall the concept of the natural rate of unemployment, the portion of the unemployment rate unaffected by the swings in the business cycle. Now we have introduced the concept of the NAIRU. How do these two concepts relate to each other?
The answer is that the NAIRU is another name for the natural rate. The level of unemployment the economy “needs” in order to avoid accelerating inflation is equal to the natural rate of unemployment.

9. Long Run Phillips Curve
Vertical curve set at NAIRU
The relationship between unemployment and inflation in the long run, after expectations of inflation have had time to adjust to experience.
Proves there are limits to expansionary policies when already at full employment