Compare methods

	Counterfactual Historical Reasoning	Historical GDP Back-Projection
Field	History	Economic History
Family	Process / pipeline	Process / pipeline
Year of origin	1964	2001
Originator	Robert Fogel (rigorous cliometric form); Max Weber and Geoffrey Hawthorn (philosophical foundations)	Angus Maddison; with indicator methods from Robert Allen, Paolo Malanima, and Jan Luiten van Zanden
Type	conceptual-analytic	descriptive-extrapolation
Seminal source	Fogel, R. W. (1964). Railroads and American Economic Growth: Essays in Econometric History. Johns Hopkins Press. ISBN: 9780801805547	Maddison, A. (2007). Contours of the World Economy 1-2030 AD: Essays in Macro-Economic History. Oxford University Press. ISBN: 9780199227204
Aliases	What-if history, Counterfactual analysis, Minimal-rewrite counterfactuals, Plausible-world reasoning	Maddison back-projection, Indicator-based GDP estimation, Retrospective GDP extrapolation, Benchmark-and-interpolation GDP
Related	3	3
Summary	Counterfactual historical reasoning is the disciplined practice of asking what would have happened had some past condition been different, in order to assess whether that condition truly mattered. Every causal claim in history, that a railway, a war, an institution, or an idea made a difference, implicitly compares the actual world to a counterfactual one in which the supposed cause is absent. Counterfactual reasoning makes that comparison explicit and subjects it to rules: alter the antecedent minimally, keep the rest of the world as it plausibly would have been, and reason carefully toward the likely consequent. In its rigorous cliometric form, exemplified by Fogel's railroads study, the consequent is quantified as a social saving. But the general method is broader and conceptual, governed by criteria of minimal rewrite, plausibility, and explicit antecedent-consequent structure, and it underwrites causal inference throughout history, not only in its quantitative, economic variant.	Historical GDP back-projection estimates long-run income for periods too thinly documented for full national accounting. Rather than rebuilding sectoral value-added year by year, it anchors to a handful of relatively secure benchmark estimates and fills the gaps between and before them using indirect indicators that move with income, chiefly the share of population living in towns, real wages of building labourers, agricultural productivity, and population density. The logic, associated above all with Angus Maddison and developed further by Allen, Malanima, and van Zanden, is that these indicators bear a stable, theoretically grounded relationship to per-capita output, so their movements can proxy GDP growth where direct measurement is impossible. The method has produced the multi-century per-capita income series that frame debates about pre-modern stagnation, Malthusian dynamics, and the European Little Divergence, while remaining explicitly more uncertain than bottom-up accounts.