Prasanta Chandra Mahalanobis, known as “PCM” to colleagues, students, and generations of those who benefited from his legacy (Illustration: C R Sasikumar) Prasanta Chandra Mahalanobis, known as “PCM” to colleagues, students, and generations of those who benefited from his legacy (Illustration: C R Sasikumar)

More than a century ago, in 1915, a young Indian Tripos student discovered that the ship in which he was to sail home had been delayed by the War. He spent most of his extra time in England in the library of King’s College, Cambridge, where a tutor introduced him to Biometrika, a leading book on theoretical statistics of the time. The young student was fascinated, and bought nine volumes of the book — which he read on the voyage back to India, and which he continued to consult even after reaching Calcutta.

That self-taught statistician, Prasanta Chandra Mahalanobis, “PCM” to colleagues, students, and generations of those who benefited from his legacy, would go on to pioneer the study of statistics in India by establishing the Indian Statistical Institute (ISI), and lay the foundations of the Indian statistical system through the National Sample Survey Office (NSSO) and the Central Statistical Organisation (CSO).

Friday, June 29, is the 125th birth anniversary of Professor Mahalanobis — a good day to understand the legacy of India’s “Plan Man”, the architect of the Second Five Year Plan.

Also read | Who was Prasanta Chandra Mahalanobis or ‘PCM’?

Prasanta Chandra Mahalanobis’s work

PCM’s outstanding research contributions include the D-squared statistic, work on the design of experiment, the large-scale sample survey, fractile graphic analysis, and operations research. Peter Hall, one of the most celebrated statisticians of the modern era, attributed the origins of ‘Bootstrap’, perhaps the most powerful technique of modern statistics, to research by Mahalanobis in the 1930s and 1940s. And yet, PCM was more than just the sum of his research. As the Polish statistician Jerzy Neyman wrote: “P C Mahalanobis was not just a professor of statistics, as there are thousands of them all over the world. Mahalanobis did more. He tried to do something effective about the problems discussed.”

Indeed, PCM envisioned statistics as “a new technology for increasing the efficiency of human effort in the wildest sense”. To take just one example — in 1926, he analysed 60 years’ data related to floods in Orissa, which led to the construction, after three decades, of the Hirakud dam on the Mahanadi.

The formal transformation of a physicist into a statistician began when, as a young professor of physics in Calcutta, Prasanta Chandra established a statistical laboratory in Presidency College in the early 1920s. The ISI started its journey in 1931 as a registered society within this statistical laboratory. It subsequently moved to Amrapali, Prasanta’s house in north Calcutta, with “Unity in Diversity” as its motto. Within two years, Prasanta had established Sankhya, the Indian Journal of Statistics, a word that means both ‘determinate knowledge’ and ‘number’.

ISI, the institute that PCM founded, was truly world class — visited, in its growing stages, by giants such as the British statistician-geneticist Sir R A Fisher, the American mathematician Abraham Wald, the Soviet mathematician Andrey Kolmogorov, and Jerzy Neyman. On a visit in 1956, China’s Zhou Enlai praised the ISI’s unique indigenous model: “We are willing to make the study in this institute as a beginning of our learning from the wisdom of India.” In 1958, the Vietnamese leader Ho Chi Minh said, “I see that we have to learn much from you.” And when the first statistical institute was established in the US under the leadership of Gertrude Cox, ISI was used as the model.

Also read | Prasanta Chandra Mahalanobis remembered with a Google doodle

PCM had unique leadership qualities that attracted the best talent around him. ISI was home to scholars like R C Bose, S N Roy, K R Nair, D B Lahiri, D Basu, R R Bahadur, and C R Rao, who is now 97, and a living legend in the statistical world. S R Srinivasa Varadhan, the only Indian-origin winner of the Abel Prize, the so-called Mathematics Nobel, completed his PhD from ISI in 1959.

To the Planning Unit in ISI, Delhi, which was established at the fag end of the Mahalanobis era, PCM brought in several stars of the future — the economists Pranab Bardhan, T N Srinivasan, B S Minhas, C Rangarajan, and of course, George Akerlof, the winner, along with Michael Spence and Joseph Stiglitz, of the Economics Nobel in 2001. Akerlof’s Nobel-winning paper, The Market for Lemons: Quality Uncertainty and the Market Mechanism, published in 1970, was initiated during his tenure at ISI.

The proximity with Rabindranath Tagore added a special dimension to the life of PCM. He accompanied Tagore as his secretary to several countries. In the first issue of the second volume of Sankhya, Tagore wrote, “These are the dance steps of numbers in the arena of time and space, which weave the maya of appearance, the incessant flow of changes that ever is and is not.” It was Tagore who coined the Bengali word for statistics: rashibijnan.

It is difficult to imagine anybody else leaving behind a legacy similar to PCM’s in one lifetime. He was a unique individual who made an extraordinary contribution to his nation and society, and his legacy, in terms of the statistical infrastructure and systems that he created and the culture of research that he established, reaches far beyond the campuses of the ISI. We, the statisticians of India, owe PCM a unique debt of gratitude.

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