Phillips curve

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For the Phillips curve in supernova astrophysics, see Phillips relationship.

The Phillips curve is a single-equation empirical model, named after A. W. Phillips, describing a historical inverse relationship between rates of unemployment and corresponding rates of inflation that result within an economy. Stated simply, decreased unemployment, (i.e., increased levels of employment) in an economy will correlate with higher rates of inflation.

While there is a short run tradeoff between unemployment and inflation, it has not been observed in the long run.[1] In 1968, Milton Friedman asserted that the Phillips curve was only applicable in the short-run and that in the long-run, inflationary policies will not decrease unemployment.[2][3] Friedman then correctly predicted that, in the 1973–75 recession, both inflation and unemployment would increase.[3] The long-run Phillips curve is now seen as a vertical line at the natural rate of unemployment, where the rate of inflation has no effect on unemployment.[4] Accordingly, the Phillips curve is now seen as too simplistic, with the unemployment rate supplanted by more accurate predictors of inflation based on velocity of money supply measures such as the MZM ("money zero maturity") velocity,[5] which is affected by unemployment in the short but not the long term.[6]


Rate of Change of Wages against Unemployment, United Kingdom 1913–1948 from Phillips (1958)

William Phillips, a New Zealand born economist, wrote a paper in 1958 titled The Relation between Unemployment and the Rate of Change of Money Wage Rates in the United Kingdom, 1861-1957, which was published in the quarterly journal Economica.[7] In the paper Phillips describes how he observed an inverse relationship between money wage changes and unemployment in the British economy over the period examined. Similar patterns were found in other countries and in 1960 Paul Samuelson and Robert Solow took Phillips' work and made explicit the link between inflation and unemployment: when inflation was high, unemployment was low, and vice versa.[8]

In the 1920s, an American economist Irving Fisher noted this kind of Phillips curve relationship. However, Phillips' original curve described the behavior of money wages.[9]

In the years following Phillips' 1958 paper, many economists in the advanced industrial countries believed that his results showed that there was a permanently stable relationship between inflation and unemployment.[citation needed] One implication of this for government policy was that governments could control unemployment and inflation with a Keynesian policy. They could tolerate a reasonably high rate of inflation as this would lead to lower unemployment – there would be a trade-off between inflation and unemployment. For example, monetary policy and/or fiscal policy could be used to stimulate the economy, raising gross domestic product and lowering the unemployment rate. Moving along the Phillips curve, this would lead to a higher inflation rate, the cost of enjoying lower unemployment rates.[citation needed] Economist James Forder argues that this view is historically false and that neither economists nor governments took that view and that the 'Phillips curve myth' was an invention of the 1970s.[10]

Since 1974, seven Nobel Prizes have been given to economists for, among other things, work critical of some variations of the Phillips curve. Some of this criticism is based on the United States' experience during the 1970s, which had periods of high unemployment and high inflation at the same time. The authors receiving those prizes include Thomas Sargent, Christopher Sims, Edmund Phelps, Edward Prescott, Robert A. Mundell, Robert E. Lucas, Milton Friedman, and F.A. Hayek.[11]


In the 1970s, many countries experienced high levels of both inflation and unemployment also known as stagflation. Theories based on the Phillips curve suggested that this could not happen, and the curve came under a concerted attack from a group of economists headed by Milton Friedman.[citation needed] Friedman argued that the Phillips curve relationship was only a short-run phenomenon. In this he followed eight years after Samuelson and Solow [1960] who wrote " All of our discussion has been phrased in short-run terms, dealing with what might happen in the next few years. It would be wrong, though, to think that our Figure 2 menu that related obtainable price and unemployment behavior will maintain its same shape in the longer run. What we do in a policy way during the next few years might cause it to shift in a definite way."[8] As Samuelson and Solow had argued 8 years earlier, he argued that in the long run, workers and employers will take inflation into account, resulting in employment contracts that increase pay at rates near anticipated inflation. Unemployment would then begin to rise back to its previous level, but now with higher inflation rates. This result implies that over the longer-run there is no trade-off between inflation and unemployment. This implication is significant for practical reasons because it implies that central banks should not set employment targets above the natural rate.[1]

More recent research has shown that there is a moderate trade-off between low-levels of inflation and unemployment. Work by George Akerlof, William Dickens, and George Perry,[12] implies that if inflation is reduced from two to zero percent, unemployment will be permanently increased by 1.5 percent. This is because workers generally have a higher tolerance for real wage cuts than nominal ones. For example, a worker will more likely accept a wage increase of two percent when inflation is three percent, than a wage cut of one percent when the inflation rate is zero.


U.S. Inflation and Unemployment 1/2000 to 4/2013

Most economists no longer use the Phillips curve in its original form because it was shown to be too simplistic.[6] This can be seen in a cursory analysis of US inflation and unemployment data from 1953–92. There is no single curve that will fit the data, but there are three rough aggregations—1955–71, 1974–84, and 1985–92—each of which shows a general, downwards slope, but at three very different levels with the shifts occurring abruptly. The data for 1953–54 and 1972–73 do not group easily, and a more formal analysis posits up to five groups/curves over the period.[1]

But still today, modified forms of the Phillips Curve that take inflationary expectations into account remain influential. The theory goes under several names, with some variation in its details, but all modern versions distinguish between short-run and long-run effects on unemployment. Modern Phillips curve models include both a short-run Phillips Curve and a long-run Phillips Curve. This is because in the short run, there is generally an inverse relationship between inflation and the unemployment rate; as illustrated in the downward sloping short-run Phillips curve. In the long run, that relationship breaks down and the economy eventually returns to the natural rate of unemployment regardless of the inflation rate.[13]





The traditional Phillips curve[edit]


Money wage determination[edit]


The "money wage rate" (W) is shorthand for total money wage costs per production employee, including benefits and payroll taxes. The focus is on only production workers' money wages, because (as discussed below) these costs are crucial to pricing decisions by the firms.








[1] gW = gWT - f(UU*) + λ·gPex.





[2] gWT = gZT.


Pricing decisions[edit]

Next, there is price behavior. The standard assumption is that markets are imperfectly competitive, where most businesses have some power to set prices. So the model assumes that the average business sets a unit price (P) as a mark-up (M) over the unit labor cost in production measured at a standard rate of capacity utilization (say, at 90 percent use of plant and equipment) and then adds in the unit materials cost.


gZ = gZT and Z = ZT.


So pricing follows this equation:

P = M × (unit labor cost) + (unit materials cost)
= M × (total production employment cost)/(quantity of output) + UMC.

UMC is unit raw materials cost (total raw materials costs divided by total output). So the equation can be restated as:

P = M × (production employment cost per worker)/(output per production employee) + UMC.

This equation can again be stated as:

P = M×(average money wage)/(production labor productivity) + UMC
= M×(W/Z) + UMC.


gP = gW - gZT.



gP = −f(UU*) + λ·gPex.


gP = −f(UU*) + λ·gPex + gUMC.




gP = [1/(1 − λ)]·(−f(UU*) + gUMC).



- f(UU*) = gUMC.


f(UU*) = 0 which implies that U = U*.



New classical version[edit]


Start with the aggregate supply function:


Note that this equation indicates that when expectations of future inflation (or, more correctly, the future price level) are totally accurate, the last term drops out, so that actual output equals the so-called "natural" level of real GDP. This means that in the Lucas aggregate supply curve, the only reason why actual real GDP should deviate from potential—and the actual unemployment rate should deviate from the "natural" rate—is because of incorrect expectations of what is going to happen with prices in the future. (The idea has been expressed first by Keynes, General Theory, Chapter 20 section III paragraph 4).


We re-arrange the equation into:

Next we add unexpected exogenous shocks to the world supply v:



where π and πe are the inflation and expected inflation respectively.

There is also a negative relationship between output and unemployment (as expressed by Okun's law). Therefore, using



New Keynesian version[edit]

The New Keynesian Phillips curve was originally derived by Roberts in 1995,[17] and since been used in most state-of-the-art New Keynesian DSGE models like the one of Clarida, Galí, and Gertler (2000).[18][19]

where . The current expectations of next period's inflation are incorporated as

NAIRU and rational expectations[edit]








Theoretical questions[edit]

The Phillips curve started as an empirical observation in search of a theoretical explanation.[citation needed] Specifically, the Phillips curve tried to determine whether the inflation-unemployment link was causal or simply correlational. There are several major explanations of the short-term Phillips curve regularity.

To Milton Friedman there is a short-term correlation between inflation shocks and employment. When an inflationary surprise occurs, workers are fooled into accepting lower pay because they do not see the fall in real wages right away. Firms hire them because they see the inflation as allowing higher profits for given nominal wages. This is a movement along the Phillips curve as with change A. Eventually, workers discover that real wages have fallen, so they push for higher money wages. This causes the Phillips curve to shift upward and to the right, as with B. Some research underlines that some implicit and serious assumptions are actually in the background of the Friedmanian Phillips curve. This information asymmetry and a special pattern of flexibility of prices and wages are both necessary if one wants to maintain the mechanism told by Friedman. However, as it is argued, these presumptions remain completely unrevealed and theoretically ungrounded by Friedman.[21]

Economists such as Milton Friedman and Edmund Phelps reject this theory because it implies that workers suffer from money illusion. According to them, rational workers would only react to real wages, that is, inflation adjusted wages. However, one of the characteristics of a modern industrial economy is that workers do not encounter their employers in an atomized and perfect market. They operate in a complex combination of imperfect markets, monopolies, monopsonies, labor unions, and other institutions. In many cases, they may lack the bargaining power to act on their expectations, no matter how rational they are, or their perceptions, no matter how free of money illusion they are. It is not that high inflation causes low unemployment (as in Milton Friedman's theory) as much as vice versa: Low unemployment raises worker bargaining power, allowing them to successfully push for higher nominal wages. To protect profits, employers raise prices.


However, other economists, like Jeffrey Herbener, argue that price is market-determined and competitive firms cannot simply raise prices.[citation needed] They reject the Phillips curve entirely, concluding that unemployment's influence is only a small portion of a much larger inflation picture that includes prices of raw materials, intermediate goods, cost of raising capital, worker productivity, land, and other factors.

Gordon's triangle model[edit]

Robert J. Gordon of Northwestern University has analyzed the Phillips curve to produce what he calls the triangle model, in which the actual inflation rate is determined by the sum of

  1. demand pull or short-term Phillips curve inflation,
  2. cost push or supply shocks, and
  3. built-in inflation.





Joke article[edit]

In 2008, Gregor Smith published a joke article in the prestigious Journal of Money, Credit and Banking titled "Japan's Phillips Curve Looks Like Japan". This article points out the uncanny resemblance between Japan's Phillips curve and the country's geographic shape.[22]

See also[edit]


  1. ^ a b c Chang, R. (1997) "Is Low Unemployment Inflationary?" Federal Reserve Bank of Atlanta Economic Review 1Q97:4-13
  2. ^ Friedman, Milton (1968). "The role of monetary policy". American Economic Review. 68 (1): 1–17. JSTOR 1831652. 
  3. ^ a b Phelan, John (23 October 2012). "Milton Friedman and the rise and fall of the Phillips Curve". Retrieved September 29, 2014. 
  4. ^ "Phillips Curve: The Concise Encyclopedia of Economics - Library of Economics and Liberty". 
  5. ^ "Velocity of MZM Money Stock". 22 December 2016. 
  6. ^ a b Oliver Hossfeld (2010) "US Money Demand, Monetary Overhang, and Inflation Prediction" International Network for Economic Research working paper no. 2010.4
  7. ^ Phillips, A. W. (1958). "The Relationship between Unemployment and the Rate of Change of Money Wages in the United Kingdom 1861-1957". Economica. 25 (100): 283–299. doi:10.1111/j.1468-0335.1958.tb00003.x. 
  8. ^ a b Samuelson, Paul A.; Solow, Robert M. (1960). "Analytical Aspects of Anti-Inflation Policy". American Economic Review. 50 (2): 177–194. JSTOR 1815021. 
  9. ^ Fisher, Irving (1973). "I discovered the Phillips curve: 'A statistical relation between unemployment and price changes'". Journal of Political Economy. The University of Chicago Press. 81 (2): 496–502. doi:10.1086/260048. JSTOR 1830534.  Reprinted from 1926 edition of International Labour Review.
  10. ^ Forder, James (2014). Macroeconomics and the Phillips Curve Myth. Oxford University Press. ISBN 978-0-19-968365-9. 
  11. ^ Domitrovic, Brain (10 October 2011). "The Economics Nobel Goes to Sargent & Sims: Attackers of the Phillips Curve". Retrieved 12 October 2011. 
  12. ^ Akerlof, George A.; Dickens, William T.; Perry, George L. (2000). "Near-Rational Wage and Price Setting and the Long-Run Phillips Curve". Brookings Papers on Economic Activity. 2000 (1): 1–60. 
  13. ^ Jacob, Reed (2016). "AP Macroeconomics Review: Phillips Curve". 
  14. ^ Blanchard, Olivier (2000). Macroeconomics (Second ed.). Prentice Hall. pp. 149–55. ISBN 0-13-013306-X. 
  15. ^ Clarida, Richard; Galí, Jordi; Gertler, Mark (1999). "The science of monetary policy: a New-Keynesian perspective". Journal of Economic Literature. American Economic Association. 37 (4): 1661–1707. doi:10.1257/jel.37.4.1661. JSTOR 2565488. 
  16. ^ Blanchard, Olivier; Galí, Jordi (2007). "Real Wage Rigidities and the New Keynesian Model". Journal of Money, Credit, and Banking. 39 (s1): 35–65. doi:10.1111/j.1538-4616.2007.00015.x. 
  20. ^ Forder, James (2010). "The historical place of the 'Friedman-Phelps' expectations critique". European Journal of the History of Economic Thought. 17 (3): 493–511. doi:10.1080/09672560903114875. 
  22. ^ Smith, Gregor W. (1 September 2008). "Japan's Phillips Curve Looks Like Japan". 40 (6): 1325–1326. doi:10.1111/j.1538-4616.2008.00160.x – via Wiley Online Library. 

Further reading[edit]

External links[edit]