With the supercommittee's deadline only five days away, the special deficit-cutting panel's chances of reaching a deal appear to be in doubt. And if no agreement is reached, more than one trillion dollars in cuts would be set in motion starting in 2013. That is, if the Congress and president allow the automatic trigger to take effect.

All of this is predicated on budget forecasting, a notoriously inaccurate art. As the CBO pointed out in a September report, an analysis based on projected baseline budgets and economic projections are “subject to a considerable degree of uncertainty.” Indeed, we ...