Prasanta Chandra Mahalanobis: the physicist who gave India its statistical foundation

Captivated by Karl Pearson's journal Biometrika, the young Bengali physicist shifted his focus from the quantum realm to data. He would go on to become the chief techno-architect of the Nehruvian state, the man who gave India its first scientific eyes and an audacious blueprint for its economic future.

Born in 1893 into an intellectually vibrant Brahmo family in Kolkata (then Calcutta), Mahalanobis was schooled at the Brahmo Boys' School. After his graduation from Presidency College, he pursued higher studies in physics at King’s College, Cambridge.

Having finished his studies and with time to kill before he left for home, Mahalanobis stumbled upon Biometrika, the first journal of modern statistics. The young physicist was instantly captivated and redirected his energies from the quantum realm to the tangible universe of human data.

Back home, in 1923, he married Nirmal Kumari, whose father was initially opposed to the wedding due to disagreements about Brahmo Samaj principles. Among those who attended the wedding were Rabindranath Tagore, who gifted the couple the manuscript of his new dance drama Basanta. The two men, despite their age gap, would become close friends. Mahalanobis wrote a series of essays titled Rabindra Parichay (Introduction to Rabindra) for the Bengali magazine Probashi.

The Mahalanobis Distance

At work, for the next 10 years, Mahalanobis taught physics by day at his alma mater, while conducting pioneering statistical research in his spare time. His early work on analyzing meteorological and anthropometric data, particularly his innovative application of statistical methods to problems of flood forecasting and crop yields, gradually built his reputation.

By the late 1920s, he had established informal statistical laboratories within Presidency College, gathering a small circle of mathematically gifted students and researchers. They would form the nucleus of what became the Indian Statistical Institute (ISI), which was formally established on 17 December 1931, in a small room in his own college quarters.

Shortly after that, he produced his most celebrated theoretical breakthrough—the Mahalanobis Distance (D²), a sophisticated measure for comparing multivariate datasets that is still used in fields ranging from machine learning to biometrics. The technique brought him international acclaim, and by the 1940s, he was recognized globally as one of the foremost statisticians of his generation.

The Mahalanobis Model

His great practical triumph, though, was the National Sample Survey (NSS) in 1950. At a time when other newly decolonized nations struggled to generate reliable economic data, Mahalanobis pioneered large-scale, nationwide sample surveys. This success made him an indispensable advisor to the government. In 1954, Prime Minister Jawaharlal Nehru appointed him an honorary statistical advisor and member of the Planning Commission.

The position would lead him to his grandest and most controversial undertaking: designing the second five-year plan. Structured around the Mahalanobis Model, the plan drew inspiration from earlier Soviet planning efforts but was adapted for India's unique scale. Its principle was simple but demanding: rather than spreading its spare resources thinly, India must make a Faustian bargain, sacrificing immediate consumption by dramatically prioritizing investments in the heavy capital goods sector over the light consumer goods sector. It stemmed from his conviction that only by building this fundamental industrial capacity could India achieve real, sustainable, long-term growth.

Yet, the very ambition of the plan led to its sharpest critique. The model's implicit assumption of a closed economy proved untenable. The massive import requirements for capital goods triggered a debilitating foreign-exchange crisis in 1957, barely a year after the plan's launch, forcing an embarrassing and painful mid-course correction. Critics, such as the economist B.R. Shenoy, wrote a Note of Dissent critiquing the plan on three grounds: its excessive size, the magnitude of deficit financing, and the policy and institutional implications.

Meanwhile, Mahalanobis’s autocratic style also bred dissatisfaction. He was accused of fostering a personality cult at the ISI and faced public dissent from his colleagues, notably the geneticist J.B.S. Haldane, who resigned, citing frustrations with the institution’s governance.

In the decades that followed, the Mahalanobis Model was officially abandoned, its legacy marred by the prolonged era of slow growth that characterized India until the liberalization of the 1990s. But while his model may have failed in practice, the institutions he built, the ISI, the NSS, and the very culture of data-driven policy, have endured and remained the bedrock upon which India’s modern economic and social policies are still constructed.

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