Accuracy of Projections

In its May 2023 budget projections for fiscal year 2024, CBO underestimated revenues by 1 percent and outlays by 6 percent. CBO’s projection of the federal budget deficit for 2024 was less than the actual amount by 1.1 percent of GDP.

CBO assesses the quality of the baseline projections of deficits and debt that it has made each spring from 1984 to 2023.

In its May 2022 projections for fiscal year 2023, CBO overestimated revenues by 11 percent and underestimated outlays by 9 percent. CBO’s projection of the federal deficit for 2023 was less than the actual amount by 3.9 percent of GDP.

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.