P. C. Mahalanobis

Prasanta Chandra Mahalanobis (1893–1972) was an Indian physicist-turned-statistician whose institutional and theoretical work shaped both the discipline of statistics in India and the architecture of Indian economic planning. Educated in physics at Presidency College, Calcutta, and at King's College, Cambridge, he returned to India and encountered Karl Pearson's journal Biometrika, which redirected his career toward statistics. He founded the Indian Statistical Institute (ISI) in Calcutta in 1931, which was later recognised as an institution of national importance by an Act of Parliament in 1959. He also established the journal Sankhyā in 1933 and was instrumental in creating the Central Statistical Organisation and the National Sample Survey. His legal and institutional legacy is dense: the ISI Act, the statutory backbone of India's official statistical system, and his appointment to the Planning Commission as an honorary member all trace directly to his initiative.

Mahalanobis's scientific contributions preceded his planning work and underpinned it. In 1936 he introduced the Mahalanobis distance, a measure of the distance between a point and a distribution that accounts for correlations among variables, now standard in multivariate statistics, classification, and anomaly detection. He pioneered large-scale sample surveys in India, developing techniques of randomised sampling, pilot surveys, and the concept of interpenetrating network of subsamples to estimate and control non-sampling error. These methods were not abstract exercises: they were built to measure crop acreage, consumer expenditure, and unemployment across a vast, statistically opaque country, giving the Indian state the empirical instruments required to plan.

The procedural core of his fame for civil-services candidates is the Mahalanobis model, a two-sector and later four-sector growth model that formed the analytical basis of the Second Five-Year Plan (1956–61). The model's central proposition is that long-run growth of consumption is maximised by directing investment toward the capital-goods sector — machines that make machines — even at the cost of suppressing consumer-goods output in the short run. In the two-sector version, the economy is divided into a capital-goods sector and a consumer-goods sector; the rate at which investment goods are allocated between the two (the parameter often denoted λ) determines the long-run trajectory of income and employment. A higher allocation to capital goods lowers immediate consumption but raises the economy's future capacity to invest, accelerating growth over a longer horizon.

The model was operationalised in concrete policy. Adopted formally by the Planning Commission under Jawaharlal Nehru, the Second Plan prioritised steel, heavy machinery, and capital-goods industries, leading to the establishment of public-sector steel plants at Bhilai, Rourkela, and Durgapur with Soviet, German, and British collaboration respectively. The Industrial Policy Resolution of 1956, which reserved commanding-height industries for the state, was the legislative companion to the Mahalanobis strategy. New Delhi's embrace of a state-led, import-substituting, capital-goods-first path defined the trajectory of the Indian economy for roughly three decades and gave the Planning Commission its intellectual identity. The four-sector elaboration added consumer-goods industries, services, and a household or small-industry sector to address employment concerns the basic model neglected.

The Mahalanobis model must be distinguished from adjacent frameworks invoked in the same examination context. It is not the Harrod-Domar model, which the First Five-Year Plan (1951–56) used: Harrod-Domar relates growth to the savings rate and the capital-output ratio without disaggregating capital and consumer goods, whereas Mahalanobis's contribution was precisely that sectoral disaggregation. It is also distinct from the Wage-Goods or Vakil-Brahmananda model, whose authors argued the binding constraint in a labour-surplus economy was the supply of consumption goods, not capital goods, and who therefore criticised the heavy-industry bias as inflationary and employment-poor. Candidates should keep the Mahalanobis distance (a statistical metric) separate from the Mahalanobis model (a growth-planning framework); both bear his name but belong to different domains.

The strategy attracted sustained criticism that remains examinable. Economists argued the capital-goods emphasis neglected agriculture and employment, generated a foreign-exchange crisis by 1957–58 as imports of machinery outran export earnings, and entrenched an inefficient, licence-bound industrial structure. The neglect of consumer goods fuelled inflationary pressure, and the model's closed-economy assumptions sat awkwardly with India's actual trade dependence. The post-1991 liberalisation, abandoning import substitution and the licence-permit system, represented a decisive repudiation of the Mahalanobis development paradigm, even as his statistical institutions endured and expanded. The dissolution of the Planning Commission in 2015 and its replacement by NITI Aayog marked the formal end of the centralised planning apparatus he helped build.

For the working practitioner and the UPSC aspirant, Mahalanobis represents the convergence of statistical capacity and state strategy that defined post-independence India. His distinction lies in being remembered both as the architect of India's official statistics — National Statistics Day is observed on his birthday, 29 June, each year — and as the economist whose model justified a generation of heavy-industry investment. Understanding him requires holding two assessments simultaneously: that his statistical methods built the empirical state, and that his growth model, however analytically elegant, produced contested developmental outcomes. For General Studies Paper III, his name anchors questions on Five-Year Plans, the public sector, and the evolution of Indian planning from Nehruvian socialism to market reform.