What it means
The intuition is about bargaining power. When almost everyone who wants work has it, employers must bid up wages to attract and keep staff, and those higher labour costs feed through into prices; when jobs are scarce, workers accept smaller rises and price pressure fades.
The original version, drawn from British wage data in the 1950s, looked like a stable trade off you could pick a point on. That confidence collapsed in the 1970s when many economies experienced high unemployment and high inflation at the same time, a combination the simple curve said should be impossible.
Economists rebuilt the idea around expectations. The modern version says inflation depends on what people already expect inflation to be, adjusted by how far unemployment sits from its sustainable level, often labelled the non accelerating inflation rate of unemployment.
Once expectations are built in, a central bank cannot buy permanently lower unemployment by tolerating permanently higher inflation. For anyone running a business, the practical relevance is in reading central bank behaviour.
When unemployment is unusually low and wage growth is accelerating, rate rises become more likely regardless of whether inflation has appeared in the published figures yet. The curve has looked notably flat in recent decades, meaning large swings in unemployment produce only small moves in inflation.
Explanations include credible inflation targeting anchoring expectations, global competition limiting price rises, and weaker collective bargaining, though no single account has settled the argument. The nuance that matters most is that expectations are the fragile part.
Once households and firms start assuming higher inflation and pricing it into wage claims and contracts, the trade off worsens sharply, which is precisely why central banks talk so insistently about keeping expectations anchored.
In practice
Real-world examples.
Example
A logistics operator sees national unemployment at a forty year low and its own drivers receiving competing offers with 9% pay rises. Anticipating rate increases, the finance director fixes the interest rate on the company's fleet financing before the next central bank meeting.
Example
An economist at a retail bank builds a simple Phillips curve model to forecast wage costs. The model correctly signals that a fall in unemployment below 4% will lift wage growth, but badly overstates how much of that reaches consumer prices.
Example
A manufacturer facing a downturn expects wage demands to soften as regional unemployment climbs. It delays its annual pay review by one quarter and settles at 3% instead of the 6% it had budgeted.
Think of it
“Phillips Curve shows unemployment and inflation trade-off-low unemployment often means higher inflation.
Formula
Calculation
A common expectations augmented form is:
Inflation = expected inflation - b x (actual unemployment rate - natural rate of unemployment)
where b measures how strongly the labour market feeds into prices.
Assume expected inflation is 2%, the natural rate of unemployment is 4.5%, and b is 0.5.
If actual unemployment falls to 3.5%, then inflation = 2% - 0.5 x (3.5% - 4.5%) = 2% - 0.5 x (-1.0%) = 2% + 0.5% = 2.5%. A tight labour market has pushed inflation half a point above expectations.
If instead unemployment rises to 6.5%, inflation = 2% - 0.5 x (6.5% - 4.5%) = 2% - 1.0% = 1.0%. Slack in the labour market has pulled inflation a full point below expectations.
Reading it in reverse tells a central bank what its policy costs. To hold inflation at 1.5% for a year with expectations at 2%, it would need unemployment at 5.5%, because 2% - 0.5 x (5.5% - 4.5%) = 1.5%, meaning roughly one percentage point of extra unemployment for half a point of disinflation.Case study
Seen in the real world.
This is an illustrative and fictional example. Merridian Freight, an invented haulage group with 900 drivers, based its three year cost plan on an assumption that pay would rise 3% a year, roughly in line with the central bank's inflation target.
Its planning team had ignored the labour market entirely. Regional unemployment for qualified drivers had fallen to around 2%, far below any sensible natural rate, and the fictional company found itself paying 11% more in year one simply to avoid losing staff to a competitor. Consumer price inflation over the same period was only 3%, so the headline number gave no warning at all.
After that shock, Merridian's finance team added a crude Phillips curve style check to its planning: when the vacancy rate for its own skill group runs far above normal, the wage assumption is raised regardless of the published inflation rate. The lesson its board took away was that the relevant labour market is the narrow one you actually recruit from, not the national average.
Watch out
Common mistakes.
- Treating the Phillips curve as a stable menu of choices, when the 1970s demonstrated that the trade off shifts as soon as expectations change.
- Assuming a flat curve means the relationship has disappeared, when it can steepen quickly once the labour market becomes extremely tight.
- Applying national unemployment figures to a specialist skill group whose own labour market may be behaving completely differently.
Questions
People also ask.
Why did the curve break down in the 1970s?
Oil supply shocks pushed prices up while output fell, and workers began building expected inflation into wage demands, producing high inflation and high unemployment together.
What is the natural rate of unemployment?
It is the level of joblessness consistent with stable inflation, made up of people between jobs and mismatches of skills, and it can only be estimated rather than measured.
Does the Phillips curve still guide central bank decisions?
It no longer dictates policy on its own, but the underlying logic that labour market slack influences inflation remains embedded in most central bank forecasting models.
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