More than a century ago, British Prime Minister Benjamin Disraeli observed, "What we anticipate seldom occurs; what we least expected generally happens." Disraeli's maxim has become a mantra for current federal spending. Every year, Congress depends on the Congressional Budget Office (CBO) to provide forecasts that will help the House and Senate set federal budget priorities for the current fiscal year and beyond. Six months later, when Congress is working on legislation that reflects these new priorities, CBO tells Congress that its forecasts were wrong. This is not acceptable. Forecasters justifiably point out that their numbers cannot be expected to...