Thoughts on the NAIRU

Simon Wren-Lewis’s post attacking Matthew Klein’s critique of the NAIRU provoked some strong reactions. On reflection, my initial response was wide of the mark. Matthew responded saying he agreed with most of Simon’s piece.

So are we all in agreement? I think there are differences, but we need to first clarify the issues.

Matthew’s main point was empirical: if you want to use a relationship between employment and inflation as a policy target it needs to be relatively stable. The evidence suggests it is not.

But there is a deeper question of what the NAIRU actually means – what is a NAIRU? The simple definition is straightforward: it is the rate of unemployment at which inflation is stable. If policy is used to increase demand, reducing unemployment below the NAIRU, inflation will rise until excess demand is removed and unemployment allowed to increase again.

At first glance this appears all but identical to the ‘natural rate of unemployment’, a concept originating with Friedman’s monetarism and inherited by some New Keynesian models – in particular the ‘standard’ sticky-price DSGE model of Woodford and others. In this view, the economy has ‘natural rates’ of output and employment, beyond which any attempt by policy makers to increase demand becomes futile, leading only to ever-higher inflation. Since there is a direct correspondence between stabilizing inflation and fixing output and employment at their ‘natural’ rates, policy makers should simply adjust interest rates to hit an inflation target. In typically modest fashion, economists refer to this as the ‘Divine Coincidence‘ – despite the fact it is essentially imposed on the models by assumption.

Matthew’s piece skips over this part of the history, jumping straight from Bill Phillips’s empirical relationship to the NAIRU. But the NAIRU is a weaker claim than the natural rate. As Simon says, all that is required for a NAIRU is a relationship of the form inf = f(U, E[inf]), i.e. current inflation is some function of unemployment and expected inflation. At its simplest, agents could just assume inflation will be the same in the current period as the last period. Then, employment above some level would causing rising inflation and vice versa.

More sophisticated New Keynesian formulations of the NAIRU are a good distance removed from the ‘natural rate’ theory – these models include imperfections in the labour and product markets and a bargaining process between workers and firms. As a result, they incorporate (at least short-run) involuntary unemployment and see inflation as driven by competing claims on output rather than the ‘too much nominal demand chasing too few goods’ story of the monetarists and simple DSGE models.

It is also the case that such a relationship is found in many heterodox models. Engelbert Stockhammer explores heterodox views on the NAIRU in a provocatively-titled paper, ‘Is the NAIRU Theory a Monetarist, New Keynesian, Post Keynesian or Marxist Theory?’. He doesn’t identify a clear heterodox position – some Post-Keynesians reject the NAIRU outright, while others present models which incorporate NAIRU-like relationships.

Engelbert notes that arguably the earliest definition of the NAIRU is to be found in Joan Robinson’s 1937 Essays in the Theory of Employment:

In any given conditions of the labour market there is a certain more or less definite level of employment at which money wages will rise … there is a certain level of employment, determined by the general strategical position of the Trade Unions, at which money wages rise, and at that level of employment there is a certain level of real wages, determined by the technical conditions of production and the degree of monopoly’ (Robinson, 1937, pp. 4-5)

Recent Post-Keynesian models also include NAIRU-like relationships. For example, Godley and Lavoie’s textbook includes a model in which workers and firms compete by attempting to impose money-wage and price increases respectively. The size of wage increases demanded by workers is a function of the employment rate relative to some ‘full employment’ level. That sounds a lot like a NAIRU – but that isn’t how Godley and Lavoie see it:

Inflation under these assumptions does not necessarily accelerate if employment stays in excess of its ‘full employment’ level. Everything depends on the parameters and whether they change … An implication of the story proposed here is that there is no vertical long-run Phillips curve. There is no NAIRU. (Godley and Lavoie, 2007, p. 304, my emphasis)

The authors summarise their view with a quote from an earlier work by Godley:

Indeed if it is true that there is a unique NAIRU, that really is the end of discussion of macroeconomic policy. At present I happen not to believe it and that there is no evidence of it. And I am prepared to express the value judgment that moderately higher inflation rates are an acceptable price to pay for lower unemployment. But I do not accept that it is a foregone conclusion that inflation will be higher if unemployment is lower (Godley 1983: 170, my emphasis).

This highlights a key difference between Post-Keynesian and neoclassical approaches to the NAIRU: where Post-Keynesian models do include NAIRU-like relationships, the relevent employment level is endogenous, due to hysteresis effects for example. In other words, the NAIRU moves around and is influenced by demand-management policy. As such, the NAIRU is not an attractor for the unemployment rate as in many neoclassical models.

Marxist theory also contains something which looks a lot like a NAIRU: the ‘industrial reserve army’ of the unemployed. Marx argued that unemployment is the mechanism by which capitalists discipline workers and prevent wage claims rising to the point at which profits and capital accumulation are depleted. Periodic recessions are therefore a necessary part of the capitalist development process.

This led Nicholas Kaldor to describe Margaret Thatcher as ‘our first Marxist Prime Minister’ – not because she was an advocate of socialist revolution but because she understood the reserve army mechanism: ‘They have managed to create a pool – or a “reserve army” as Marx would have called it – of 3 million unemployed … the British working classes have been thoroughly cowed and frightened.’ (This point is passed over rather quickly in Simon’s piece. In the 1980s, he writes, ‘policy changed and increased unemployment and inflation fell.’)

So we should be careful about blanket dismissals of the NAIRU. Instead, we must be clear how our analysis differs: what are the mechanisms which generate inflationary pressure at low levels of unemployment – conflicting claims or excess nominal demand? Is the NAIRU stable and exogenous? Does it act as an attractor for the unemployment rate, and over what time period? What are the implications for policy?

Ultimately, I think this breaks down into an issue about semantics. How far from the unique, stable, vertical long-run Phillips curve can we get and still have something we call a NAIRU? Simon adopts a very loose definition:

There is a relationship between inflation and unemployment, but it is just very difficult to pin down. For most macroeconomists, the concept of the NAIRU really just stands for that basic macroeconomic truth.

I’d like to believe this were true. But I suspect most macroeconomists, trained on New Keynesian DSGE models, have a narrower view: they tend to think in terms of a stable short-run sticky-price Phillips curve and a unique long-run Phillips curve at the ‘natural’ rate of employment.

There is one other aspect to consider. Engelbert Stockhammer distinguishes between the New Keynesian NAIRU theory and the New Keynesian NAIRU story. He argues (writing in 2007, just before the crisis) that the NAIRU has been used as the basis for an account of unemployment which blames inflexible labour markets, over-generous welfare states, job protection measures and strong unions. The policy prescriptions are then straightforward: labour markets should be deregulated and welfare states scaled back. Demand management should not be used to reduce unemployment.

While economists have changed their tune substantially in the decade since the financial crisis, I suspect that the NAIRU story is one reason that defence of the NAIRU theory generates such strong reactions.

EDIT: Bruno Bonizzi points me to this piece at the INET blog with has an excellent discussion of the empirical evidence and theoretical implications of hysteresis effects and an unstable NAIRU.


Image reproduced from Wikipedia:



  1. It’s finally political. NAIRU people are just arguing for keeping a fraction of the work force unemployed.

    So I cannot agree with the statement:

    Ultimately, I think this breaks down into an issue about semantic

    It also creates deep fears in the minds of politicians and prevents them from even attempting to reach full employment.

    Liked by 1 person

    1. Joan Robinson is arguing that wage-price spirals can happen. Talking about a possibility is different than claiming something is certain, ie NAIRU.

      So claiming she invented NAIRU is too much.


  2. What I find completely disingenuous about any NAIRU particulars, generally agreed by the mainstream, is that there is precisely zero public, media or political discussion of it, or its serious impact on public policy.

    To the inevitable percentage of unemployed, where NAIRU informs policy, an explanation and public apology is seriously due, in my opinion, to those unfortunates for whom no job exists.

    Instead, the opposite is permitted to be the mainstream view right across society. If the victims are not blamed directly, then governments routinely deny any policy responsibility for perpetually high rates of unemployment. At minimum, in recent decades, economies operate with no job for 1 in 20 of the workforce. The average, with any consideration of under employment, and official under estimation (for political optics) would be mostly double that figure.

    Yet the jobless are condemned to poverty and deprived over generations of life opportunity. Ultimately for near zero responsibility of their own. This is the real scandal of NAIRU, and I look upon those continuing this public deception with utter contempt. And that is the entirety of the mainstream economics profession and academe.


  3. What do you think about search models of unemployment?
    I always thought they sound very sensible…

    I think the simplest model would be:

    A fraction x of all firms go out of business every month
    All employees find a job after s months.

    In this world unemployment would be close to x*s (the exact math is more complicated, but I don’t think it adds much)…

    so if 1% of firms go out of business every month and it takes 3 months to find a new job, unemployment would be around 3%.

    I am not saying this is realistic model as there are more issue than I want to list here, but the basic idea seems sound: in an economy where firms go out of business, there needs to be a positive unemployment level unless job search is istantaneous (even for people with no job history).

    If you add imperfect information, heterogenous agents and other issues, you’d likely get much higher numbers (but it depends).

    In this simple world it’s not a percentage of workers who is unemployed: every worker spends a percentage of his working life in unemployment while searching for a job.

    A separate point is wherever NAIRU is exogenous for the central bank. This is a separate issue from the economy overall. Even if you agree that NAIRU is endogenous to the economy, you can argue the central bank has no tools to modify NAIRU directly (e.g. in the search model above, demand is assumed to be stable). This does require a different monetray policy than under the assumption of stable NAIRU as the signal from the unemployment rates becomes weaker. Does it mean that under a fully stochastic NAIRU, you should become an inflation targeter? I am not smart enough to work it out…


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