2 ms·Efficiency assumes rational players. When bubbles happen there isn't much rationality available.by steveplace 18y agoEfficiency assumes rational players. When bubbles happen there isn't much rationality available.eru 18y agoThe problem seems to be that rationality is not common knwowledge.eru 18y agoIn the technical sense of game theory: Everyone knows that everyone knows (and so one) that everyone is rational. That is different from everyone being rational individually, but not knowing that the others are.