Thanks for the link. Ellenberg gives a great analogy to stock prices and points out something important: the study measured the absolute expected deviation for the predictors, but measured the expected absolute deviation for the reporters.

This difference can explain the observed discrepancy between the two groups without invoking the "end of history illusion" because .

This difference came about because obtaining an X+10-year-old's report of current personality is equivalent to drawing a random sample from an X-year-old's distribution of actual future personality, but the X-year-olds' are providing point-estimates (of something like the mean) from their distributions of predicted future personality.