Imperfect Knowledge, Inflation Expectations, and Monetary Policy


Athanasios Orphanides

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2002-04 | May 1, 2002

This paper investigates the role that imperfect knowledge about the structure of the economy plays in the formation of expectations, macroeconomic dynamics, and the efficient formulation of monetary policy. Economic agents rely on an adaptive learning technology to form expectations and continuously update their beliefs regarding the dynamic structure of the economy based on incoming data. The process of perpetual learning introduces an additional layer of dynamic interactions between monetary policy and economic outcomes. We find that policies that would be efficient under rational expectations can perform poorly when knowledge is imperfect. In particular, policies that fail to maintain tight control over inflation are prone to episodes in which the public’s expectations of inflation become uncoupled from the policy objective and stagnation results, in a pattern similar to that experienced in the United States during the 1970s. More generally, we show that policy should respond more aggressively to inflation under imperfect knowledge than under perfect knowledge.

Article Citation

Orphanides, Athanasios, and John C. Williams. 2002. “Imperfect Knowledge, Inflation Expectations, and Monetary Policy,” Federal Reserve Bank of San Francisco Working Paper 2002-04. Available at

About the Author
John C. Williams served as President and Chief Executive Officer of the Federal Reserve Bank of San Francisco from March 1, 2011 to June 17, 2018. Dr. Williams was previously the executive vice president and director of research for the San Francisco bank, which he joined in 2002. He began his career in 1994 as an […] Learn more about John C. Williams