Lucas Critique

The argument

In the 1960s governments simulated policy using Keynesian macroeconometric models with hundreds of equations (see Keynesian economics). In "Econometric Policy Evaluation: A Critique" (1976), Robert Lucas argued that the method was fundamentally flawed. The parameters of consumption or investment functions depend on how people expect future policy to behave, and when the policy rule changes, those expectations and decision rules change too. Holding coefficients estimated under old policies fixed while simulating new ones therefore yields systematically wrong answers. Jacob Marschak (1953) anticipated the idea, but Lucas combined it with rational expectations to drive a methodological shift in macroeconomics and received the 1995 Nobel Prize in economics.

The Phillips curve and policy implications

The leading example is the Phillips curve. In the 1960s, slightly higher inflation was thought to buy permanently lower unemployment, but when policymakers exploited it, people came to expect higher inflation, and the 1970s brought stagflation, with high inflation and high unemployment together. Sargent and Wallace (1975) proposed the "policy ineffectiveness proposition" that systematic monetary policy cannot affect real output under rational expectations, and Kydland and Prescott (1977) argued that discretionary policy suffers from time inconsistency, stressing the value of rules. Because it holds that policy effects depend on economic structure and expectations, the Lucas critique is also related to Goodhart's law.

Methodological influence and empirical debate

After the Lucas critique, macroeconomics moved toward microfoundations, building models from "deep parameters" such as preferences, technology and constraints that do not change with policy. Kydland and Prescott's (1982) real business cycle model and later DSGE (dynamic stochastic general equilibrium) models such as Smets and Wouters (2007) are prominent examples and have become standard tools at central banks. Sims (1980), however, called the restrictions of structural models "incredible" and proposed vector autoregressions instead. How much the critique matters in practice is debated: Favero and Hendry (1992) and Ericsson and Irons (1995) found that coefficients in many reduced-form models did not shift much across policy changes, and Rudebusch (2005) argued its effect may be small for typical monetary policy shifts. Chetty (2009) proposed a "sufficient statistics" approach bridging structural and reduced-form methods.

FAQ

Does the Lucas critique mean econometric models are useless?

No. It means models should be built on structural elements that do not change with policy, which led to the development of models with microfoundations.

Has the Lucas critique been confirmed empirically?

The evidence is mixed. Cases like the breakdown of the Phillips curve in the 1970s fit well, but several studies report that reduced-form relationships were fairly stable across ordinary policy changes.

Sources reviewed: 2026-10-26

References

1. Lucas, R. E. (1976). Econometric policy evaluation: A critique. Carnegie-Rochester Conference Series on Public Policy, 1, 19–46.
2. Marschak, J. (1953). Economic measurements for policy and prediction. In W. C. Hood & T. C. Koopmans (Eds.), Studies in Econometric Method (pp. 1–26). New York: Wiley.
3. Muth, J. F. (1961). Rational expectations and the theory of price movements. Econometrica, 29(3), 315–335.
4. Sargent, T. J., & Wallace, N. (1975). 'Rational' expectations, the optimal monetary instrument, and the optimal money supply rule. Journal of Political Economy, 83(2), 241–254.
5. Kydland, F. E., & Prescott, E. C. (1977). Rules rather than discretion: The inconsistency of optimal plans. Journal of Political Economy, 85(3), 473–492.
6. Kydland, F. E., & Prescott, E. C. (1982). Time to build and aggregate fluctuations. Econometrica, 50(6), 1345–1370.
7. Sims, C. A. (1980). Macroeconomics and reality. Econometrica, 48(1), 1–48.
8. Favero, C., & Hendry, D. F. (1992). Testing the Lucas critique: A review. Econometric Reviews, 11(3), 265–306.
9. Ericsson, N. R., & Irons, J. S. (1995). The Lucas critique in practice: Theory without measurement. In K. D. Hoover (Ed.), Macroeconometrics (pp. 263–312). Boston: Kluwer.
10. Rudebusch, G. D. (2005). Assessing the Lucas critique in monetary policy models. Journal of Money, Credit and Banking, 37(2), 245–272.
11. Smets, F., & Wouters, R. (2007). Shocks and frictions in US business cycles: A Bayesian DSGE approach. American Economic Review, 97(3), 586–606.
12. Linde, J. (2001). Testing for the Lucas critique: A quantitative investigation. American Economic Review, 91(4), 986–1005.
13. Chetty, R. (2009). Sufficient statistics for welfare analysis: A bridge between structural and reduced-form methods. Annual Review of Economics, 1, 451–488.