Lucas aggregate supply function: Difference between revisions

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The '''Lucas aggregate supply function''' or '''Lucas''' "'''surprise'''" '''supply function''', based on the '''Lucas imperfect information model''', is a modelrepresentation of [[aggregate supply]] based on the work of [[New classical macroeconomics|new classical]] economist [[Robert Lucas, Jr.|Robert Lucas]]. The model states that [[economic output]] is a function of "money" or "price "surprise"." The model accounts for the empirically based trade off between output and prices represented by the [[Phillips curve]], but the function breaks from the Phillips curve since only unanticipated price level changes lead to changes in output.<ref>{{cite book |first=Olivier Jean |last=Blanchard |author-link=Olivier Blanchard |first2=Stanley |last2=Fischer |author-link2=Stanley Fischer |chapter=The Lucas Model |title=Lectures on Macroeconomics |___location=Cambridge |publisher=MIT Press |year=1989 |isbn=978-0-262-02283-5 |chapter-url={{Google books |plainurl=yes |id=j_zs7htz9moC |page=358 }} |pages=356–360 [p. 358] }}</ref> The model accounts for empirically observed short-run correlations between output and prices, but maintains the [[neutrality of money]] (the absence of a price or money supply relationship with output and employment) in the long-run. The [[Policy Ineffectiveness Proposition|policy ineffectiveness proposition]] extends the model by arguing that, since people with [[rational expectations]] cannot be systematically surprised by [[monetary policy]], monetary policy cannot be used to systematically influence the economy.

== Background ==

New classical economics made its first attempt to model aggregate supply in Lucas and [[Leonard Rapping]] (1969).<ref>Snowdon{{Cite journal | jstor = 1808963|title=Price Expectations and Vanethe (2005)Phillips Curve|author1=Robert E. Lucas, 233Jr.|author2= Leonard A. Rapping|journal=The American Economic Review|volume=59|number= 3|date=June 1969|pages= 342–350}}</ref> In this earlier model, supply (specifically labor supply) is a direct function of real wages: Moremore work will be done when real wages are high and less when they are low. Under this model, unemployment is "voluntary.".<ref name="SnowdonVane233">Snowdon and Vane (2005), 233.</ref> In 1972 Lucas made a second attempt at modelling aggregate demandsupply.<ref>Snowdon andname="SnowdonVane233" Vane (2005), 233.</ref> This attempt drew from [[Milton Friedman]]'s [[natural rate hypothesis]] that challenged the Phillips curve.<ref name="SnowdonVane453">Snowdon and Vane (2003), 453.</ref> Lucas supported his original, theoretical paper that outlined the surprise based supply curve with an empirical paper that demonstrated that countries with a history of stable price levels exhibit larger effects in response to monetary policy than countries where prices have been volatile.<ref>Snowdon andname="SnowdonVane453" Vane, 453.</ref>

On the basis of Lucas' 1973 paper,<ref>{{cite journal|last1=Lucas|first1=Robert|title=Some international evidence on output-inflation tradeoffs|journal=American Economic Review|date=1973|volume=63|issue=3|pages=326–334}}</ref> [[Thomas Sargent]] and [[Neil Wallace]] introduced their 'surprise' supply function in which there was a white noise error term introduced that cannot be predicted in any way.<ref>{{cite journal|last1=Sargent|first1=Tom|last2=Wallace|first2=Neil|title=Rational" expectations, the optimal monetary instrument, and the optimal money supply rule|journal=Journal of Political Economy|date=1975|volume=83|issue=2|pages=241–254|doi=10.1086/260321}}</ref> Lucas introduced the effects of nominal and real shocks affecting a macro-economy into his system through price expectations: if expectations are true, output in any given period is at its natural level. However, the well-known and widely accepted aggregate production function described by Sargent and Wallace also provides leeway for the white-noise shocks independent of price expectations–resulting in the accidental nature of equilibrium and in the inefficacy of countercyclical efforts of monetary policy.<ref>{{cite book |last=Galbács |first=Peter |title=The Theory of New Classical Macroeconomics. A Positive Critique |___location=Heidelberg/New York/Dordrecht/London |publisher=Springer |year=2015 |isbn= 978-3-319-17578-2 |doi=10.1007/978-3-319-17578-2 |series=Contributions to Economics }}</ref>

Lucas's model dominated new classical economic business cycle theory until 1982 when [[real business cycle theory]], starting with [[Finn E. Kydland]] and [[Edward C. Prescott]],<ref>{{Cite journal | last1 = Kydland | first1 = F. E. | last2 = Prescott | first2 = E. C. | title = Time to Build and Aggregate Fluctuations | journal = Econometrica | volume = 50 | issue = 6 | pages = 1345–1370 | doi = 10.2307/1913386 | year = 1982 | jstor = 1913386 }}</ref> replaced Lucas's theory of a money driven business cycle with a strictly supply based model that used technology and other real [[Shock (economics)|shocks]] to explain fluctuations in output.<ref>Snowdon and Vane (2005), 295.</ref>

== Theory ==

The rationale behind Lucas's supply functiontheory centers on how suppliers get information. Lucas claimed that suppliers had to respond to a "signal extrationextraction" problem when making decisions based on prices; the firms had to determine what portion of price changes in their respective industries reflected a general change in nominal prices (inflation) and what portion reflected a change in real prices for inputs and outputs.<ref name="SnowdonVane233-34">Snowdon and Vane (2005), 233-234233–234.</ref> Lucas hypothesized that suppliers know their own industries better than the general economy. Given this imbalance in information, a supplier could perceive a general increase in prices due to inflation as an increase the [[Relative price|relative price]] for its output, reflecting a better, real price for its output and encouraging more production. The surprise leads to an increase in production and employment throughout the economy.<ref>Snowdon andname="SnowdonVane233-34" Vane (2005), 233-234.</ref>

The function can be represented simply as:

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:<math>Y_s = f(P-P_{expected})</math>

The simple version models aggregate output as a function of the price surprise. A more complicated expression of the Lucas supply curve adds expectations to the model. Aggregate supply is a function of the natural[[Potential rateoutput|“natural” level of output]] (<math>Y_{N_t}</math>) and the difference between actual prices (<math>P_t</math>) and the expected price level given past information <math>\Omega_{t-1}</math> times a coefficient based on an economy's sensitivity to price surprises (<math>\alpha</math>):<ref>Snowdon and Vane (2005), 234.</ref>

:<math>Y_s = Y_{N_t} + \alpha [ P_t - E\left(P_t | \Omega_{t-1} \right) ] </math>

By invoking [[Okun's law]] to express the function in terms of unemployment, Lucas's supply function can be viewed as an expression of the expectations-augmented Phillips curve.<ref>Snowdon and Vane (2005), 235.</ref>

==Citations==

{{reflist}}

== See also ==

* [[Lucas islands model]]

== References ==

{{reflist|30em}}

== Further reading ==

* {{cite book | last = Snowdon | first = Brian |first2=Howard R. |last2=Vane | title = An Encyclopedia of Macroeconomics | url = https://archive.org/details/encyclopediaofma00bria | url-access = registration | publisher = E. Elgar| ___location = Aldershot | year = 2002 | isbn = 978-1-84542-180-9 }}

* {{cite book | last = Snowdon | first = Brian |first2=Howard R. |last2=Vane | title = Modern Macroeconomics | publisher = E. Elgar | ___location = Cheltenham | year = 2005 | isbn = 978-1-84542-208-0 }}

* {{cite book |last=Turnovsky |first=Stephen J. |author-link=Stephen J. Turnovsky |title=Methods of Macroeconomic Dynamics |publisher=MIT Press |edition=Second |year=2000 |isbn=978-0-262-20123-0 |pages=[https://archive.org/details/methodsofmacroec0002turn/page/97 97–104] |url=https://archive.org/details/methodsofmacroec0002turn/page/97 }}

[[Category:New classical macroeconomics]]