How Do We Predict Inflation?

Ken Houghton notes that playing with data is dangerous.

Predicting the future tends to be easy. There are several ways to do it. First, you can predict that everything will grow as it did this year—or last year, or the mean of the past x years. Or you can predict that it will be great if a Republican is in office, but horrible if a Democrat is. (Call this The Kudlow Effect.)

Or, you can just predict that everything next year will be the same as it is this year.

This appears to be fairly close to what consumers do, judging by this scatterplot of annual inflation (i.e., inflation over the previous twelvemonth) against the University of Michigan’s median expectation from consumer surveys.

So the “Rational Agent” believes that nothing will change. Comments?