The Congressional Budget Office produces the official economic and budget projections that Congress uses for lawmaking. CBO forecasts shape fiscal policy debates, influence market expectations for deficits and debt, and provide a baseline against which legislation is scored. Understanding how CBO forecasts work—and their inherent limitations—helps investors interpret fiscal policy developments.
What the CBO Does
Core Functions
Budget projections: 10-year forecasts of federal spending, revenues, and deficits under current law.
Economic projections: Forecasts of GDP, inflation, interest rates, and employment that underpin budget estimates.
Cost estimates (scoring): Analysis of how proposed legislation would change spending and revenues relative to baseline.
Long-term projections: 30-year outlooks for major entitlement programs and debt sustainability.
Independence and Credibility
The CBO is nonpartisan by design:
- Director appointed by Congress (not the President)
- Staff are career professionals, not political appointees
- Methodology is transparent and documented
- Estimates are not influenced by whether they favor or oppose pending legislation
Key point: Both parties criticize CBO when estimates don’t support their preferred policies, but no credible alternative scoring entity exists.
The Budget Outlook Report
Publication Schedule
| Report | Timing | Content |
|---|---|---|
| Budget and Economic Outlook | January/February | Full 10-year baseline |
| Update | August | Revised projections mid-fiscal year |
| Long-Term Budget Outlook | June | 30-year debt trajectory |
| Cost Estimates | Ongoing | Scoring of pending legislation |
Anatomy of a Baseline Projection
FY2024 CBO Baseline (illustrative):
| Category | FY2024 | FY2034 (10-year) |
|---|---|---|
| Total revenues | $4.9 trillion | $6.5 trillion |
| Total outlays | $6.9 trillion | $9.5 trillion |
| Deficit | $2.0 trillion | $3.0 trillion |
| Debt held by public | $28 trillion | $48 trillion |
| Debt-to-GDP | 99% | 122% |
What “current law” means: The baseline assumes:
- Expiring tax provisions actually expire
- Discretionary spending follows caps or statutory limits
- Entitlement formulas remain unchanged
- No new legislation is enacted
Why this matters: Current law projections often differ from likely outcomes. TCJA individual provisions expire in 2025—the baseline assumes they expire, but most observers expect extension.
Economic Assumptions
Key Variables
CBO’s budget projections depend on economic forecasts:
| Variable | Typical 10-Year Assumption |
|---|---|
| Real GDP growth | 1.8-2.0% long-term average |
| Inflation (CPI) | 2.3-2.5% |
| 10-year Treasury yield | 4.0-4.5% |
| Unemployment rate | 4.5-5.0% NAIRU |
Sensitivity Analysis
Small changes in economic assumptions create large budget effects:
| Variable Change | 10-Year Budget Impact |
|---|---|
| GDP 0.1% higher annually | -$350 billion deficit |
| Interest rates 0.1% higher | +$300 billion deficit |
| Unemployment 0.1% lower | -$100 billion deficit |
| Inflation 0.1% higher | +$50 billion deficit |
Key insight: CBO deficit projections are more sensitive to interest rate assumptions than any other variable. Higher-for-longer rates significantly worsen long-term fiscal outlook.
CBO Track Record
Short-Term Accuracy
CBO economic forecasts are reasonably accurate over 1-2 years:
| Metric | Average Error (1-year ahead) |
|---|---|
| Real GDP growth | ±1.0 percentage points |
| Inflation | ±0.5 percentage points |
| Unemployment | ±0.5 percentage points |
| Deficit | ±$100-200 billion |
Long-Term Limitations
Accuracy deteriorates significantly beyond 2-3 years:
| Projection Period | Typical Error Range |
|---|---|
| 1 year | ±10-15% of actual |
| 5 years | ±25-40% of actual |
| 10 years | ±40-60% of actual |
Why long-term projections miss:
- Recessions are unpredictable (CBO assumes no recessions in baseline)
- Legislative changes alter the baseline
- Interest rate paths are uncertain
- Productivity trends shift unexpectedly
Historical Examples
2001 projections: CBO projected $5.6 trillion in cumulative surpluses over 10 years. Reality: $6.1 trillion in cumulative deficits (driven by 2001/2003 tax cuts, Iraq/Afghanistan, 2008 crisis).
2008 projections: CBO projected $200 billion deficit for FY2009. Reality: $1.4 trillion deficit (financial crisis effects).
Lesson: Baseline projections are not predictions—they’re mechanical calculations of current law trajectories.
How Legislation Is Scored
The Scoring Process
When Congress considers new legislation:
- Bill text is provided to CBO
- CBO estimates changes to spending and revenues vs. baseline
- Score is released (often within days of request)
- Score influences legislative debate and vote counting
Dynamic vs. Static Scoring
Static scoring: Assumes legislation doesn’t change economic behavior or GDP.
Dynamic scoring: Incorporates macroeconomic feedback effects (e.g., tax cuts may boost growth).
Current practice: CBO provides dynamic scores for major legislation since 2015. The differences are usually modest (5-15% of static cost) but can be politically significant.
Scoring Limitations
CBO scores have known blind spots:
What CBO can estimate well:
- Direct spending changes (clear appropriations)
- Tax rate changes with historical precedent
- Entitlement formula modifications
What CBO struggles with:
- Behavioral responses to new policies
- State and local government reactions
- Long-term productivity effects
- Innovation and R&D spillovers
Using CBO Projections
For Market Analysis
What CBO reports tell you:
- Direction and magnitude of fiscal trends
- Sensitivity of deficits to interest rates
- Relative size of budget components
- Timeline for trust fund depletion
What CBO reports don’t tell you:
- What Congress will actually do
- When or if markets will react to fiscal trends
- Optimal policy responses
Investor Checklist
When CBO releases projections:
- Note changes from previous baseline (better or worse?)
- Check interest rate assumptions vs. current market rates
- Identify key drivers of deficit changes
- Review economic growth assumptions for reasonableness
- Note any special factors (e.g., COVID relief phase-out)
When legislation is scored:
- Compare CBO score to sponsor claims
- Note whether dynamic or static scoring used
- Identify key assumptions driving the estimate
- Assess likelihood of passage given fiscal impact
Common Pitfalls
Pitfall 1: Treating projections as predictions
CBO baselines assume current law continues and no recessions occur. Neither is realistic over 10 years.
Pitfall 2: Ignoring the economic assumptions
A projection showing stable deficits may assume declining interest rates—check the underlying economics.
Pitfall 3: Comparing across different baselines
CBO updates its baseline frequently. Comparing a 2023 estimate to 2024 projection requires adjusting for baseline changes.
Pitfall 4: Overweighting long-term numbers
The 10th year of a projection has enormous uncertainty. Focus on near-term estimates and trends rather than specific far-future numbers.
Summary
CBO provides the authoritative baseline for federal budget analysis, but projections are not predictions. Short-term estimates are reasonably accurate; long-term projections are highly uncertain. Interest rate assumptions are the largest sensitivity. Investors should use CBO reports to understand fiscal trends and policy debates while recognizing that actual outcomes will differ—often substantially—from baseline projections.
Related Articles
- Budget Deficits, Surpluses, and Debt-to-GDP
- Fiscal Multipliers and Output Gaps
- Tracking Appropriations and Continuing Resolutions
References
Congressional Budget Office (2024). The Budget and Economic Outlook: 2024 to 2034.
CBO (2023). CBO’s Economic Forecasting Record: 2023 Update.
Auerbach, A. (2019). Fiscal Policy. Handbook of Macroeconomics.
