Accuracy of Projections

In this report, CBO uses various measures to assess the quality of its past projections of federal outlays. The analysis focuses on three fiscal years within each projection period: the budget year, the 6th year, and the 11th year.

The Congressional Budget Act of 1974 requires CBO to produce an annual report on federal spending, revenues, and deficits or surpluses. This document provides answers to questions about how CBO prepares those baseline budget projections.

In its July 2021 projections for fiscal year 2022, CBO underestimated revenues by 10 percent and outlays by 5 percent. CBO’s projection of the federal budget deficit for 2022 was more than the actual amount by 0.8 percent of GDP.

The average error for CBO’s budget-year revenue projections is 1.2 percent, indicating the agency has tended to slightly overestimate revenues. For the agency’s sixth-year revenue projections, the average error is greater—5.6 percent.

CBO analyzes its baseline projections of deficits and debt held by the public that were made each year beginning in 1984. In this report, CBO reviews its projections for the first and fifth years after the fiscal year already under way.

In 2009, the Recovery Act boosted monthly benefits for SNAP. The resulting increase in spending on SNAP benefits from 2009 to 2013 was greater than CBO had estimated. This report discusses that underestimate and the reasons for it.

In the baseline projections CBO has issued each spring, projected outlays have generally been close to actual amounts, although they have been too high, on average—a consequence of the agency’s economic forecasts and other factors.

CBO's revenue projections since 1982 have, on average, been a bit too high—more so for projections spanning six years than for those spanning two—but their overall accuracy has been similar to that of the projections of other agencies.