Guess ⅔ of the Average

A legendary puzzle used in economics experiments and quant interviews — it measures how many steps ahead people actually think.

Everyone in a large group picks a whole number from 0 to 100.

The winner is whoever's guess is closest to two-thirds (⅔) of the average of all the guesses.

Everyone is trying to win, and everyone knows that everyone is trying to win.

What number should you pick?

(Answer with a single number.)