You knew it all along: Economists can't forecast the economy worth a hoot. And now we have a scholarly study that confirms it. Better yet, the corroboration comes from an impeccable source: the Federal Reserve.

The study compared predictions of important economic indicators — unemployment, inflation, interest rates, gross domestic product — with the actual outcomes. There were widespread errors. The study concluded that "considerable uncertainty surrounds all macroeconomic projections."

Just how large were the mistakes? The report, though written mostly in technical jargon, gives a straightforward example: