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Which think tanks and academic studies provided 2024 estimates of net fiscal impact and how do their methodologies differ?
Executive summary
Multiple U.S. think tanks and official budget agencies produced 2024-era estimates of fiscal impacts; prominent contributors in the material supplied include seven organizations convened by the Peter G. Peterson Foundation (American Action Forum, AEI, Bipartisan Policy Center, Center for American Progress, Economic Policy Institute, Manhattan Institute, Progressive Policy Institute) whose plans were revenue‑scored by the Tax Policy Center, as well as government scorekeepers and fiscal monitors such as the Congressional Budget Office, Office of Management and Budget, and the IMF, which publish baseline and scenario projections [1] [2] [3] [4] [5] [6]. Methodological differences center on (a) baseline choice and policy counterfactuals, (b) time horizons and inclusion of longer‑run debt dynamics, (c) whether supply effects, multipliers and term‑premium feedbacks are modelled, and (d) the use of revenue scoring versus macroeconomic fiscal‑impact measures [2] [7] [8] [9] [5].
1. Who produced 2024 estimates — a quick roll call
The Peterson Foundation’s Solutions Initiative asked seven leading U.S. policy organizations to publish 30‑year plans; the Tax Policy Center produced revenue scores for each plan and news coverage summarized how each think tank reduced projected deficits over 30 years (American Action Forum, AEI, Bipartisan Policy Center, Center for American Progress, Economic Policy Institute, Manhattan Institute, Progressive Policy Institute) [1] [2] [10]. Separately, official analysts — CBO and OMB — carried their routine baseline projections and analytical perspectives for FY2024 and the 2024–2034 outlook, while the IMF produced Fiscal Monitor material that assesses fiscal risks and term‑premium feedbacks [3] [4] [6] [8].
2. Baselines and counterfactuals: the core methodological dividing line
Think tanks’ numbers depend on the baseline and counterfactual they choose: the Peterson Foundation project asked each group to propose policy packages and the Tax Policy Center scored the revenue elements against a common revenue scoring framework — but the think tanks themselves used different mixes of spending cuts, tax changes, and reform priorities to reach deficit reductions, producing materially different fiscal outcomes despite a common scoring on revenues [2] [10] [1]. By contrast, CBO and OMB publish standardized “current‑law” baselines and sensitivity re‑estimates (Analytical Perspectives), which provide a common yardstick for debt and deficit projections [3] [4].
3. Horizon, accounting and what gets counted
Think‑tank plans in the Solutions Initiative were evaluated over a 30‑year window; the Tax Policy Center provided revenue scores on those proposals with that long horizon in mind [2] [10]. CBO’s Budget and Economic Outlook typically provides 10‑year projections with additional long‑run discussion; OMB’s Analytical Perspectives contains intertemporal analyses and sensitivity exercises [3] [4]. The IMF’s Fiscal Monitor adds another perspective, highlighting how fiscal choices affect term premiums and international spillovers over medium horizons [6] [8].
4. Macroeconomic feedbacks, multipliers and supply effects — who includes what
Methodologies diverge on macro feedbacks: Brookings’ Hutchins Center Fiscal Impact Measure explicitly measures direct demand effects of fiscal policy (discretionary and automatic stabilizers) and flags when it excludes fiscal multipliers; other measures (IMF analysis) estimate how deficits can raise term premiums and global borrowing costs using econometric term‑premium estimation methods (Adrian‑Crump‑Moench) [7] [8]. The Peterson Foundation exercise relied on the Tax Policy Center for revenue scoring, which applies standard static and dynamic scoring procedures to revenue proposals — but the think tanks’ supply‑side claims and spending multipliers were heterogeneous across memos [2] [10].
5. Transparency, reporting conventions and implicit agendas
Public agencies (CBO, OMB, IMF) publish detailed methodologies and appendices (CBO outlook, OMB Analytical Perspectives, IMF Fiscal Monitor methodology), enabling reproducibility and cross‑comparison [3] [4] [6]. Think tanks vary in transparency of underlying behavioral assumptions: the Peterson Foundation convening made memos public and had TPC score revenues, but each organization framed priorities differently — some emphasize tax increases, others spending restraint or growth‑oriented investments — reflecting ideological priorities that shape methodological choices [1] [2].
6. How to read differences in estimates — what they tell readers
Divergent fiscal outcomes between think tanks do not necessarily imply arithmetic error; they reflect choices about what to include (tax vs. spending focus), time horizon, whether and how macro feedbacks are modelled, and baseline assumptions about policies that will or will not occur under “current law” [2] [10] [3]. Official baselines (CBO/OMB) are the standard reference for lawmakers, while think‑tank packages illustrate policy alternatives and tradeoffs scored by third parties like the Tax Policy Center [3] [4] [2].
7. Limitations and next steps for readers
Available sources do not list every methodological footnote for each of the seven think‑tank memos in this dataset; readers seeking granular replication should consult the individual memos, the Tax Policy Center revenue scores, and the CBO/OMB methodological appendices cited above for line‑by‑line assumptions [2] [10] [4] [3] [6].