Sims has published numerous important papers in his areas of research: econometrics and macroeconomic theory and policy. Among other things, he was one of the main promoters of the use of vector autoregression in empirical macroeconomics. He has also advocated Bayesian statistics, arguing for its power in formulating and evaluating economic policies.
Sims has been an outspoken opponent of the rational expectations revolution in macroeconomics, arguing that it should be thought of as a "cautionary footnote" to econometric policy analysis, rather than "a deep objection to its foundations." He has been similarly skeptical of the value of real business cycle models.
On October 10, 2011, Christopher A. Sims together with Thomas J. Sargent was awarded the Nobel Memorial Prize in Economic Sciences. The award cited their "empirical research on cause and effect in the macroeconomy". His Nobel lecture, titled "Statistical Modeling of Monetary Policy and its Effects" was delivered on December 8, 2011.
Translating his work into everyday language, Sims said it provided a technique to assess the direction of causality in central bank monetary policy. It confirmed the theories of monetarists like Milton Friedman that shifts in the money supply affect inflation. However, it also showed that causality went both ways. Variables like interest rates and inflation also led to changes in the money supply.