We consider social learning in a changing world. With changing states, societies can remain responsive only if agents regularly act upon fresh information, which drastically limits the value of observational learning. When the state is close to persistent, a consensus whereby most agents choose...

We consider a political agency model where voters learn information about some policy-relevant variable, which they can ignore when it impedes their desire to hold optimistic beliefs. Voters' excessive tendency to sustain optimism may result in inefficient political decision-making because...