Are consistent expectations better than rational expectations ?

Elliot Aurissergues (1)

1 PSE - Paris School of Economics

In this paper, I argue that agents may prefer learning a misspecified model instead of learning the rational expectation model. I consider an economy with two types of agent. Fundamentalists learn a model where endogenous variables depend on relevant exogenous variables whereas followers learn a model where endogenous variables are function of their lagged values. A Fundamentalist is like a DSGE econometrician and a follower is like a VAR econometrician. If followers (resp. fundamentalists) give more accurate forecasts, a fraction of fundamentalists (resp. followers) switch to the follower model. I apply this algorithm in a linear model. Results are mixed for rational expectations. Followers may dominate in the long run when there are strategic complementarities and high persistence of exogenous variables. When additionnal issues are introduced, like structural breaks or unobservable exogenous variable, followers can have a significant edge on fundamentalists. I apply the algortihm in three economic models a cobweb model, an asset price model and a simple macroeconomic model.

Mots clés: cobweb model; consistent expectations; Adaptive learning

Domaines: Economies et finances

Elliot Aurissergues. Are consistent expectations better than rational expectations ?. 2017. ⟨hal-01558223v2⟩