Paul Narcyz Rosenstein-Rodan, La complementarietà: prima delle tre tappe del progresso della teoria economica pura (1933)

Rosenstein-Rodan’s theoretical and historical journal article reconstructs complementarity as the first of three advances beyond the marginalist foundations of 1871; non-measurability and time remain subjects for subsequent studies. Its nineteen sections move from an introductory account of marginal utility through mathematical and non-mathematical treatments to a concluding synthesis. Against both claims that pure economics is complete and declarations that it needs wholesale refoundation, Rosenstein-Rodan presents theoretical progress as the systematic revision of inherited assumptions.

Complementarity here encompasses all dependence among utilities, including substitution and rivalry as well as mutually reinforcing wants. General interdependence in demand is insufficient: utility itself depends on the availability and employment of other goods. The decisive conceptual move is therefore from the utility of a good to the utility of its particular uses. With several interdependent goods, their best uses cannot already be given; discovering them constitutes the economic problem.

Allo scopo di scegliere l'impiego ottimo, cioè per accertare il miglior uso dei beni, se ne confrontano le utilità; questo è il significato del piano economico.

English translation: To choose the optimal employment, that is, to ascertain the best use of goods, their utilities are compared; this is the meaning of the economic plan.

Section A credits Edgeworth’s indifference curves with replacing independent utility schedules by a joint utility function, then distinguishes three phases in Pareto’s thought. Rosenstein-Rodan accepts the importance of indifference analysis but contests the later attempt to make utility logically subsequent to choice. An extended discussion of Davenport, Wicksteed, Knight, Croce, Kaufmann, Mises, and Fetter separates theories explaining choices through prior valuations from those deriving valuations from choices. His objection turns on anticipated rather than realized utility:

Poichè in ogni modo, con gli atti meditati e sistematici, l'anticipazione dell'utilità precede la scelta.

English translation: For in any case, with deliberate and systematic acts, the anticipation of utility precedes choice.

For planned conduct, imagined alternatives must be evaluated before action. Defining utility through completed choices risks tautology; taking demand curves as primitive narrows the explanatory task. Virtual choices likewise require comparisons of anticipated utilities. Rosenstein-Rodan’s separate objection to indifference analysis is methodological: it constructs equilibrium without describing how individuals discover their preferred arrangements. The distinction between mathematical and non-mathematical economics concerns explanatory aims, not the use of symbols.

Section B traces the gradual recognition of general complementarity. Earlier Austrian theories chiefly treated complementary goods as a special problem of imputation. Komorzynski, Voigt, and Sulzer instead examined interdependent uses within an economic plan, anticipating developments later rediscovered by the new Vienna school. Wicksteed and Knight recognized relative utility and interconnected schedules but did not fully specify the ordering of comparisons through which a plan emerges. Engländer’s compensating combinations clarify substitution, yet leave the formation of marginal relationships insufficiently explained.

Hans Mayer and Leo Schönfeld supply the central distinction between the formation of an entire allocation and subsequent modifications of it. Marginal utilities emerge from a completed plan before becoming guides to later adjustment. Schönfeld treats total economic utility as unknown, while individual utilities express perceptible changes in it. Immediate utility holds other uses fixed; mediated utility allows their advantageous rearrangement. Rosenstein-Rodan nevertheless acknowledges Hayek’s objection: improvements may require coordinated changes across several goods, although each isolated change reduces utility. Schönfeld’s simplest sequential comparisons therefore do not conclusively settle the general problem.

The practical culmination is abbreviated economic calculation. Experience preserves much of an existing plan, permitting selective adjustment rather than exhaustive reconsideration. Rosenstein-Rodan formulates its exchange rule precisely:

Di qui ecco la legge del calcolo economico abbreviato: nella ponderazione per lo scambio si paragona sempre l'utilità mediata del bene di cui si mette in esame l'acquisto con l'utilità immediata dell'altro di cui si mette in esame la rinuncia (1).

English translation: Hence the law of abbreviated economic calculation: in deliberating an exchange, one always compares the mediated utility of the good whose acquisition is under consideration with the immediate utility of the other whose relinquishment is under consideration (1).

The full theoretical reconstruction explains the experience that makes this shortcut possible; experience cannot itself serve as the ultimate explanation without circularity. The article’s significance lies in connecting general complementarity to the formation of plans and to the economy of deliberation. Its preferred synthesis retains equilibrium analysis while demanding an account of how valuations arise and become usable guides to conduct.