Vertical Long-Run Phillips Curve

The vertical long-run Phillips curve is the macroeconomics idea that, in the long run, inflation and unemployment do not trade off. It shows unemployment returning to its natural rate no matter what inflation does.

What is the Vertical Long-Run Phillips Curve?

In Principles of Macroeconomics, the vertical long-run Phillips curve is the graph that says there is no lasting tradeoff between inflation and unemployment. In the long run, the economy moves back to its natural rate of unemployment, so changing inflation does not permanently change unemployment.

That is why the curve is drawn vertically at the natural rate. It keeps the same unemployment level on the horizontal axis while inflation can vary along the vertical axis. The message is simple: you might be able to push unemployment down for a while, but the economy does not stay there forever just because inflation rose.

This idea is the long-run counterpart to the short-run Phillips curve. The short-run version can slope downward, which creates the tempting policy tradeoff you see in many graphs and class examples. But once workers and firms adjust their expectations, wages, prices, and contracts catch up, and unemployment returns to its normal long-run level.

The vertical shape comes from classical economic thinking. In the long run, output and employment are pinned by real factors like technology, labor force participation, and market frictions, not by the inflation rate. So if the central bank expands the money supply and inflation rises, the economy may move along the short-run curve for a while, but it does not get a permanent unemployment boost.

A good way to picture it is this: suppose policymakers try to use expansionary monetary policy to cut unemployment below its natural rate. At first, lower interest rates and higher spending can increase demand. Over time, though, inflation expectations rise, firms raise prices, and the unemployment rate drifts back to where it started. The result is higher inflation, not a new long-run unemployment level.

This is why the vertical long-run Phillips curve matters whenever the course asks what monetary policy can and cannot do. It separates short-run effects from long-run outcomes and reminds you that the long-run economy is not controlled by inflation in the same way the short run is.

Why the Vertical Long-Run Phillips Curve matters in Principles of Macroeconomics

This term shows up whenever you compare short-run policy effects with long-run macro outcomes. It explains why a central bank can sometimes lower unemployment for a little while, but cannot keep unemployment below the natural rate just by creating more inflation.

That distinction is a big part of reading Phillips curve graphs correctly. If a prompt gives you a policy shift, a rise in inflation expectations, or a return to long-run equilibrium, the vertical long-run Phillips curve tells you what happens after the short-run movement fades.

It also helps with the logic of monetary policy. In macro, money growth can affect nominal variables like the inflation rate, but the long-run unemployment rate is determined by real features of the economy. Once you know that, you can explain why inflation policy and unemployment policy do not move together forever.

A lot of confusion comes from treating the short-run tradeoff as permanent. This term keeps you from making that mistake and gives you a clean way to explain why the economy can adjust back even after a demand shock or policy change.

How the Vertical Long-Run Phillips Curve connects across the course

Phillips Curve

The vertical long-run Phillips curve is the long-run version of the Phillips Curve idea. The broader Phillips Curve starts with the inverse short-run relationship between unemployment and inflation, but the vertical long-run curve says that relationship does not last once expectations and wages adjust. Together, they show why the same graph can tell two different stories depending on the time frame.

Natural Rate of Unemployment

The vertical line sits at the natural rate of unemployment, so this term and that one go together. In the long run, unemployment returns to that rate even if inflation changes. If you can identify the natural rate in a graph or scenario, you can usually place the long-run Phillips curve correctly.

Adaptive Expectations

Adaptive expectations help explain why the short-run tradeoff disappears. If people form expectations from past inflation, they gradually adjust wages and prices after inflation rises. That adjustment shifts the short-run Phillips curve and brings unemployment back to its natural rate, which is why the long-run curve is vertical.

NAIRU

The Non-Accelerating Inflation Rate of Unemployment is closely related to the natural rate idea. It is the unemployment rate consistent with stable inflation in the long run. When you see NAIRU in a macro question, think of it as the unemployment level that lines up with the vertical long-run Phillips curve.

Is the Vertical Long-Run Phillips Curve on the Principles of Macroeconomics exam?

A quiz question may show a Phillips curve graph and ask you to identify the long-run position, or to explain why a policy that lowers unemployment in the short run does not keep working. The right move is to say that the economy returns to the natural rate of unemployment, while inflation changes along the vertical curve.

In an essay or short response, you might be asked to explain a central bank action. Use this term to show that expansionary policy can raise inflation, but it cannot permanently reduce unemployment below the natural rate. If the prompt includes rising inflation expectations, connect that adjustment to the return to long-run equilibrium.

Key things to remember about the Vertical Long-Run Phillips Curve

• The vertical long-run Phillips curve says there is no permanent tradeoff between inflation and unemployment.

• It is drawn vertically at the natural rate of unemployment, because unemployment returns there in the long run.

• This concept explains why expansionary policy may lower unemployment temporarily, but not forever.

• Rising inflation can change nominal outcomes, but it does not create a lasting drop in unemployment.

• If you see a Phillips curve graph, the long-run version tells you what happens after expectations and wages adjust.

Frequently asked questions about the Vertical Long-Run Phillips Curve

What is the Vertical Long-Run Phillips Curve in Principles of Macroeconomics?

It is the long-run version of the Phillips Curve, showing no lasting tradeoff between inflation and unemployment. The curve is vertical because unemployment returns to the natural rate in the long run. Inflation can change, but the long-run unemployment rate does not move with it.

Why is the long-run Phillips curve vertical?

It is vertical because, over time, workers, firms, and policymakers adjust their expectations. As wages and prices catch up, unemployment moves back to its natural rate. That leaves inflation as the variable that changes, not the long-run unemployment rate.

How does the vertical long-run Phillips curve differ from the short-run Phillips curve?

The short-run Phillips curve can slope downward, showing a temporary tradeoff between inflation and unemployment. The long-run curve is vertical, showing that the tradeoff disappears after expectations adjust. A policy that works in the short run does not necessarily work in the long run.

How do you use the vertical long-run Phillips curve on a macro quiz?

Look for questions about long-run equilibrium, natural unemployment, or the limits of monetary policy. If the prompt asks what happens after inflation rises, say unemployment returns to the natural rate while inflation stays higher. If it asks about policy, say the curve shows no permanent unemployment gain from higher inflation.