 And, in a suitable twist of intellectual fate, macroeconomists have recently begun to explore the question of whether sunspot expectations can provide a more plausible source of fluctuations in dynamic equilibrium models than the conventional aggregate productivity disturbances.Cass’s third major contribution to economic theory was his work on general equilibrium with incomplete markets, work which grew out of his exploration of the question of existence of sunspot equilibria in models with incomplete asset markets.Cass’s follow-on work on existence and determinacy of general equilibrium in models with incomplete asset markets spawned another large literature which has come to be known simply as GEI.