Driving the 480 miles from Columbus, Ohio to Raleigh, N.C., should take you about eight hours. But what if your GPS device insisted you could make the trip in four? Blindly following such an unreliable estimate, even when made by your trusted GPS, would cause you a lot of problems.

Congress too often makes the mistake of blindly following projections of the Congressional Budget Office that later prove to be grossly inaccurate. The CBO’s reputation among the public and the media may be strong, but its track record in providing accurate estimates to Congress leaves much to be desired.