Economists who adhere to rational-expectations models of the world will never admit it, but a lot of what happens in markets is driven by pure stupidity - or, rather, inattention, misinformation about fundamentals, and an exaggerated focus on currently circulating stories.

Each profession has its own toolkit.

My clinical psychologist wife of 40 years has always had a close intellectual influence on me. When I was beginning to talk openly in the economics profession about irrationality in decision-making, I received a lot of criticism. Ginny would support my views and remind me that a whole other profession - psychology - studies people's irrational sides.

Some of the best theorizing comes after collecting data because then you become aware of another reality.

A major boom in real stock prices in the US after Black Tuesday brought them halfway back to 1929 levels by 1930. This was followed by a second crash, another boom from 1932 to 1937, and a third crash. Speculative bubbles do not end like a short story, novel, or play. There is no final denouement that brings all the strands of a narrative into an impressive final conclusion. In the real world, we never know when the story is over.

Somehow, talking to young students brings you back to reality - it should, anyway.

Consider our difficulties avoiding junk food and overspending. Such addictions were carefully planned-for by professional marketing teams.