One can count on Gilles Saint-Paul for innovative research topics. During his career, he has addressed and impressive array of topics that range far beyond Economics strictu sensu. For this reason, I have reported several times about his latest research.
His latest opus is an introspection in our profession and how our political biases influence our modelling choices. He claims that an economist with conservative inclinations will favor a model with smaller fiscal multipliers. While the ethical thing to do would be to be driven by empirical evidence, this may just be a subconscious choice. But at least economists strive to be logically consistent, and if one choose a large multiplier, then then must also claim that demand shocks are substantial, as models with large multipliers rely on this. Looking at evidence from the Survey of Professional Forecasters, Saint-Paul finds that forecasters who believe that expansions are more inflationary also adhere to the belief that public expenses are less expansionary.
Saint-Paul goes further, though. His claim is that we live in a self-confirming equilibrium. We devise theories to understand our surrounding and take decisions, and those decisions then shape the economic environment. Theories can thus survive even if they deviate from the true structure as long as the decisions make it conform. This is a statement about a lack of uniqueness of the path to the rational expectations equilibrium. In a sense, this is not too disturbing, as long as decisions are still optimal and outcomes do not differ too much from the rational expectations first best. And if this true, we will never know what the rational expectations first best is. Of broader implications would be if the political agenda of an economist would lead an economy on an different path, on a different self-confirming equilibrium. Is this why Europe and the United States are different? Were Keynes and von Hayek that influential?