Why do we rely on the CBO when its numbers are so easy to game?

The CBO’s rules make it hard for the group to fulfill its own mandate. You’d think, for example, that the CBO would use its own parameters when it crunches numbers. Instead, the CBO must use the same mathematical assumptions supplied by the very lawmakers who wrote the bill the group is evaluating. No matter how improbable those formulas are.

Former CBO director Douglas Holtz-Eakin, writing in the New York Times, described the group’s process as “fantasy in, fantasy out.”

CBO rules often preclude common sense. Its forecasters can’t take into account any other legislation when studying the price tag of a proposed bill. That enabled the forecasters costing out House Speaker Nancy Pelosi’s bill to overlook this fact: Medicare spending increases will force tax increases, which in turn will hurt growth.

This dynamic is permitted because the answers the CBO supplies make it easier for politicians to sell their bills. They’re happy. And so, for the moment, are voters who are painfully aware that the U.S. federal budget can’t cover new entitlements, yet accept such legislation as a balm for that pain.