Rational and Near‐Rational Bubbles Without Drift

Rational and Irrational Bubbles

Endogenous Rational Bubbles

A weighted replicator dynamic describes how agents switch between a forecast based on fundamentals, a rational bubble forecast and a re‡ective forecast, a weighted average of the former two. If the innovations to the extraneous martingale have a similar magnitude to those of the dividend process and agents are su¢ ciently aggressive in switching forecasting strategies, a signi…cant portion of t...

Injecting rational bubbles

This paper proves two theorems about economies with a finite number of infinitely lived agents who trade a complete set of one-period Arrow securities and several infinitely lived securities at each date, subject to short-sales constraints. The first theorem in the paper considers an equilibrium to an economy of this kind. It proves that there exists another economy with perturbed short-sales c...

Rational Equity Bubbles

People use to believe that no bubble can exist in an infinite-horizon model with a finite number of rational individuals. However, the opinion is true only for the baseline case. In the baseline model, wealth merely provides consumption flows, which individuals only care about. No one likes to hold an asset, whose price is above its fundamental value, forever. Sooner or later, individuals will ...

Bubbles are rational

As we show using the notion of equilibrium in the theory of infinite sequential games, bubbles and escalations are rational for economic and environmental agents, who believe in an infinite world. This goes against a vision of a self regulating, wise and pacific economy in equilibrium. In other words, in this context, equilibrium is not a synonymous of stability. We attempt to draw from this st...