Michał Kalecki

Kalecki's most original theoretical contribution is the profit equation. Starting from national income accounting identities and assuming workers do not save, he derived the elegant relation that total profits (P) equal the sum of capitalists' consumption (Cp) and gross investment (I): P = Cp + I. From this Kalecki established the direction of causation. Capitalists may decide to invest and consume more but cannot decide to earn more, so it is investment and consumption decisions that determine profits. Investment thus determines saving, not the reverse. This insight is summarized in the aphorism: "workers spend what they get, and capitalists get what they spend."

Kalecki then built a theory of income distribution. Assuming firms operate in imperfectly competitive, particularly oligopolistic, markets where they set prices by applying a mark-up over variable costs, the wage share in national income (α) depends on the economy-wide average mark-up (k) and the ratio of raw material costs to wages (j). The mark-up is determined by the "degree of monopoly," the ease with which firms can raise prices without losing demand. Kalecki explained an empirical regularity: over the business cycle, the wage share remains roughly constant. During recessions, firm collusion raises the degree of monopoly, but falling raw material prices offset this; during booms, stronger union bargaining power reduces monopoly power, but rising raw material prices counteract it.

Together, the profit equation and income distribution theory represent an original synthesis integrating Marx's theory of surplus value with Keynes's principle of effective demand in a single mathematical framework. By placing class-based income distribution at the center of macroeconomic dynamics, Kalecki decisively influenced post-Keynesian and neo-Marxian economics, most notably Baran and Sweezy's Monopoly Capital.

Kalecki's 1963 book 'Introduction to the Theory of Growth in a Socialist Economy' (Zarys teorii wzrostu gospodarki socjalistycznej) is an original mathematical analysis of long-run growth in centrally planned economies. In it he established the fundamental equation in which the national income growth rate is determined by three variables: the productive accumulation rate, investment efficiency (the capital-output coefficient), and depreciation. Kalecki's core insight is that while raising the accumulation rate accelerates growth, it does so at the cost of current consumption; thus the government must use the 'government decision curve' to select an optimal balance between intergenerational equity and growth.

He systematically analyzed the constraints on socialist growth: limits to labor supply, foreign trade bottlenecks (when export revenues must finance imported investment goods), and the difficulty of organizational and technical transformation. Kalecki took 'uniform growth' (sustained growth at a constant rate) as the reference path, and showed that accelerating the accumulation rate temporarily raises the growth rate but inevitably triggers a labor shortage and a subsequent 'deceleration' phase in which growth converges back to the reference path. This provided theoretical grounds for criticizing the unrealism of Soviet-style 'hurrah planning.'

Kalecki's growth theory served as the methodological foundation for the 1961–1975 Perspective Plan he directed in Poland, but the authorities rejected his cautious growth targets as 'defeatist' and pursued politically-driven over-investment. This experience taught him that even under planning, political will can override rational economic analysis. The work influenced development planning in Cuba, India, and Israel, and with its 1972 English translation gained recognition in the West as a classic of socialist growth theory.