The 1971 Census of India is a foundational concept in Indian polity, not an act, institution, or scheme, but a decennial population count that became a fixed benchmark for political representation and resource allocation. It was the third census conducted in independent India, following the 1951 and 1961 censuses, and recorded a population of 547,949,809 people. The census itself is a systematic collection and analysis of demographic and socio-economic data, conducted under the provisions of the Census Act, 1948.
The census's enduring significance stems from its connection to the constitutional process of delimitation, which is the fixing of the number of seats and boundaries of territorial constituencies for the Lok Sabha and State Legislative Assemblies. Originally, Articles 82 and 170 of the Constitution mandated that the number of seats be readjusted after every census based on the latest population figures. However, the 42nd Amendment Act, 1976, froze the allocation of seats in the Lok Sabha and State Assemblies to the states based on the 1971 Census figures.
This mechanism was created to solve the problem of uneven population growth, which would have penalized states that successfully implemented population control measures by reducing their political representation. By freezing the seat allocation, the government aimed to incentivize population stabilization. The freeze was initially set until the year 2000 but was extended by the 84th Amendment Act, 2001, until the first census after 2026.
The 1971 Census figures are also used to determine the value of votes for Members of Parliament (MPs) and Members of Legislative Assemblies (MLAs) in the Presidential election, as stipulated in Article 55 of the Constitution. While the number of seats remains frozen at the 1971 level, the boundaries of the constituencies were later redrawn by the Delimitation Commission based on the 2001 Census figures, as empowered by the 87th Amendment Act, 2003, without altering the total number of seats allotted to each state. The core provision that the state-wise allocation of seats is based on the 1971 Census has stayed the same since 1976, but the use of the 2001 Census for internal constituency boundary rationalization was a recent change.