My, what a discussion we have generated. On rationality, I am always surprised that economists think there is any thought process associated with rationality. At best it is a Hobbesian pain/pleasure principle. In practice, whatever people do is defined as rational (we don't ask why they do it as psychologists would); the question is to explain why anyone similarly situated would behave in the same way. Perhaps we ought to ban "rationality" from the vocabulary of economics; it misleads because it implies something that it does not. Fred Carstensen