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What percentage of US federal budget goes to defense spending?
Executive Summary
The best synthesis of the provided analyses shows that defense spending has recently represented roughly 12–16% of total U.S. federal outlays, with commonly cited point estimates clustering near 12–13% for FY2023–FY2024 and a larger DOD-budgetary-resources share reported for FY2025. Differences arise from varying definitions (total defense outlays vs. Department of Defense budgetary resources vs. national-security–related spending) and from whether analysts compare defense to total federal outlays or to discretionary spending alone [1] [2] [3] [4]. Readers should treat any single percentage as a snapshot tied to a given fiscal year and accounting definition rather than a fixed, timeless fact [5] [6].
1. What claimants said and where they diverge — a clear map of the arguments
Multiple claims appear in the analyses. One prominent claim reports about one-sixth of federal spending goes to national defense, reflecting a CBO framing that places defense near 16–17% of outlays [4]. Another analysis cites about 20% as a representative share in some summaries or context discussions, often conflating broader “defense and security” totals or using different base budgets [6]. Several data-driven sources converge on ≈12–13% for FY2023–FY2024: USAFacts reports 12.9% in FY2024 [1], CBO-derived arithmetic gives ≈12.3% using $850 billion defense / $6.9 trillion total outlays [2], and USAFacts/other trackers list ~13.3% for 2023 [5] [7]. A contrasting figure shows the Department of Defense accounting for 15.8% of FY2025 federal budgetary resources because that series uses DoD-specific budgetary-resources totals [3]. These differences reflect choice of numerator and denominator, not arithmetic mistakes.
2. Which numbers are apples and which are oranges — definitions that change the headline
The variations stem from different accounting definitions. Some sources count only discretionary national defense outlays (traditional defense appropriation lines), while others include broader national-security programs, classified budgets, veterans’ benefits, or emergency war supplemental funding; this raises the numerator [6] [2]. The denominator likewise varies: analysts sometimes divide by total federal outlays (all mandatory and discretionary spending), sometimes by total discretionary spending, and sometimes by narrower “budgetary resources” measures used by specific agencies, producing different percentages [3] [2]. The analytical choice materially shifts the headline: defense as a share of discretionary spending will be much larger than defense as a share of total federal outlays. Any cited percentage should be reported with the exact accounting basis and fiscal year attached [1] [2].
3. Recent fiscal-year snapshots — what the empirical record shows for 2023–2025
For the most recent fiscal years covered by the analyses, FY2023 and FY2024 figures cluster near 12–13% of total federal outlays: USAFacts reports 12.9% for FY2024 [1], other trackers list 13.3% for 2023 [5], and CBO-derived totals produce ≈12.3% when dividing CBO’s defense outlays estimate ($850 billion) by FY2024 total outlays (~$6.9 trillion) [2]. For FY2025, a different framing shows the Department of Defense’s $1.71 trillion in budgetary resources representing 15.8% of that fiscal-year federal budget presentation, reflecting inclusion of additional budgetary items beyond core discretionary defense outlays [3]. These snapshots show a recent downward trend from higher shares in earlier decades and substantial year-to-year volatility tied to supplemental funding and total outlay changes [1] [5].
4. Historical context and international comparisons that clarify, not confuse
Historically, defense’s share of the federal budget has ranged widely, peaking during wartime and shrinking in peacetime; long-run data show defense’s share has been as high as about 90% in some wartime years and below 11% in some recent years, with the modern post‑Cold War norm often between ~10–20% [1]. Internationally, the United States spends more in absolute dollars than any other country but ranks differently when measured as a share of GDP; military spending near 3–3.4% of GDP appears in World Bank series for recent years, which is a different metric than defense’s share of federal outlays [8]. Both comparisons are useful but answer different policy questions: budget-priority debates use share of federal outlays, while strategic-capability debates often use percent of GDP.
5. Why the debate matters — policy, politics, and transparency issues to watch
Percentages feed policy debates because how you count affects perceived priorities: a 12–13% figure of total outlays presents defense as a significant but not dominant category, while 15–20% claims or one-sixth framings suggest a heavier prioritization. These framing choices carry political utility: advocates of increased defense funding highlight broader national-security lines and supplemental requests; critics emphasize total outlays and rising mandatory spending elsewhere. Transparency issues persist around classified budgets, emergency supplements, and definitions used by different agencies. A responsible citation should state the fiscal year, numerator and denominator, and whether the figure includes supplements, veterans’ benefits, or related security programs [1] [2] [3].