The Cambridge tradition: Kaldor, Robinson and Pasinetti

In the neoclassical models the split of income between wages and profits follows from technology: with a Cobb–Douglas function, capital gets its marginal product, a share α. Saving is assumed to be a fixed fraction of total income, and growth comes from technology or preferences.

In the Cambridge models the logic runs the other way. Growth is given (by Harrod’s natural rate or by the investment that firms plan), the saving rates of different classes are given, and the distribution of income adjusts until saving equals the investment needed. Nicholas Kaldor, Joan Robinson, Luigi Pasinetti and Piero Sraffa belonged to the tradition. They emphasised, in different ways, that capitalists’ spending decisions drive the economy and that profits are what capitalists save.

Let output Y be split into wages W and profits P, and let workers save a share s_w of wages and capitalists a share s_c of profits, with s_c > s_w. Total saving is S = s_wW + s_cP. At full employment, the economy must invest I to grow at the target rate, and saving must equal investment. Divide by Y and write P/Y = π:

Here is the surprise. The profit share depends on the investment share and the two saving rates, and not on the production function. If the economy needs to invest more to grow faster, saving has to rise, and the only way is to shift income towards the group that saves more, the capitalists. Faster growth means a higher profit share (Kaldor 1955–56). It is the reverse of the neoclassical claim that distribution is set by technology.

The chart plots the profit share against the investment share. Move the capitalists’ and workers’ saving rates, the growth rate and the capital–output ratio, and watch the profit share and the profit rate. Notice what the Pasinetti line in the readouts does when you change workers’ saving.

Kaldor’s workers save out of wages but, in effect, never own capital. Pasinetti (1962) noticed that workers who save accumulate wealth, and wealth earns profits. If workers lend to firms, they receive a share of profit income, and the rate of profit earned by every owner of capital is the same. He showed that in the long run, with growth at rate g, the profit rate is

The workers’ saving rate does not appear. Workers’ savings raise the share of capital they own but not the profit rate, which is pinned down by the capitalists’ saving rate and the growth rate alone. The Pasinetti paradox is that thrift of the working class does not lower the rate of profit, and it also does not depend on the production function: contrary to the neoclassical idea that more saving lowers the return on capital. Samuelson and Modigliani (1966) showed that the result holds in a range of cases but that a second regime exists, when workers’ saving is high enough, in which the capitalists’ saving rate no longer fixes the profit rate.

Joan Robinson’s The Accumulation of Capital (1956) extended Keynes to the long run and Harrod to the question of distribution. Her central benchmark is the golden age: steady growth with full employment, in which the capital stock is fully used and grows at the natural rate, and the rate of profit is constant. It is called golden because it is an ideal that actual economies seldom reach. She contrasted it with states in which growth is held back by the lack of investment or by the lack of workers.

Do not confuse the two golden things. Robinson’s golden age is a growth path. Phelps’s golden rule (Lesson 7) is a saving rate. Solow’s steady state is a third thing, a state where per-worker variables are constant. UGC NET 2026 gave all three names in one question and asked which attributions are right: Solow for the steady state, Robinson for the golden age, Phelps for the golden rule of accumulation.

Joan Robinson (1953–54) asked a pointed question about the aggregate production function Y = F(K, L): in what units is K measured? Physical machines differ and cannot be added up, so K has to be measured in value. But the value of a machine depends on the rate of profit used to discount its future earnings, and the rate of profit is supposed to be determined by the marginal product of capital. The reasoning is circular: capital cannot be measured without knowing distribution, and distribution cannot be explained without knowing capital.

Piero Sraffa’s Production of Commodities by Means of Commodities (1960) provided the tools, and the debate produced the puzzle of reswitching. A technique of production can be the cheapest at a low rate of profit, be replaced by another as the rate of profit rises, and then become the cheapest again at a still higher rate. If that can happen, there is no simple relationship between the rate of profit and the quantity of capital per worker. The neoclassical parable, in which a lower profit rate always goes with more capital per worker, can fail.

Samuelson (1966) accepted that reswitching and the related “capital reversing” are logically possible, a concession that was taken as a victory for the English Cambridge side. The practical outcome was more modest: economists have continued to use aggregate production functions, as in the models of this module, treating them as approximations. Cohen and Harcourt (2003) review what became of the argument.

Kaldor also pressed an empirical case that manufacturing is the engine of growth. Three relationships, usually called Kaldor’s laws, summarise it. In the notation of UGC NET 2025 (g_m for the growth of manufacturing output, g_gdp for GDP growth, P_m and P_om for productivity in and outside manufacturing):

In the same match question Okun’s law is the link between unemployment and output, and not one of Kaldor’s. Thirlwall (1983) is the standard guide to the laws. Kaldor’s argument was also an argument about causation, the same point made in the passage JNU sets in a comprehension question: capital endowment cannot explain the wealth of nations, since capital accumulation and the growth of output are “different aspects of a single process”, and industrial development can change capital endowment.

P. C. Mahalanobis (1953) wrote a growth model for a planned economy. The economy has two sectors: a capital-goods sector, whose output is machines, and a consumption-goods sector. A planner chooses the share λ_k of investment going to the capital-goods sector. A unit of capital there raises output by β_k, in the other sector by β_c. Machines are produced only by the capital-goods sector, so investment next year can grow only as fast as that sector expands: investment grows at λ_kβ_k. Income rises by β̄ = λ_kβ_k + λ_cβ_c per unit of investment.

The Second Five-Year Plan (1956–61) followed this strategy, with priority for heavy and basic industry, and the Industrial Policy Resolution of 1956 was framed alongside it. Exams ask for the plan’s name and emphasis (JAM 2023, 2026; Hyderabad 2011; CUET 2018). The criticisms of the strategy, and its results, belong in the Indian economy pages, since they depend on facts and figures outside this model. Mahalanobis’s own paper is the source for the model.

Questions on Kaldor’s laws and passage, the Second Plan and the Mahalanobis model, and the authors of the Cambridge works, from JNU, UGC NET, JAM, Hyderabad and CUET-PG. The Delhi School’s class-saving economy is in Lesson 14.