Constitutional Amendments Governing Delimitation

Delimitation is the process of readjusting territorial constituencies to reflect population changes recorded by a census. The Constitution ordinarily connects this exercise with each census, but the 42nd, 84th and 87th Amendments postponed seat reallocation while permitting limited boundary readjustment.

Basic constitutional scheme

Under Article 82, Parliament provides by law for readjustment of Lok Sabha representation and constituencies after each census. Article 170 similarly governs the composition and territorial constituencies of state legislative assemblies, while Articles 330 and 332 concern seats reserved for Scheduled Castes and Scheduled Tribes.

Changes made by the three amendments

• The 42nd Amendment Act, 1976 froze the readjustment of Lok Sabha seats among states and state assembly representation on the basis of the 1971 Census until the relevant figures of the first census after 2000 were published.
• The 84th Amendment Act, 2001 extended this freeze until the relevant figures of the first census taken after 2026 are published. It nevertheless permitted constituency boundaries and SC and ST reserved seats to be readjusted using the 1991 Census, without changing the number of seats allocated to a state or the total strength of its assembly.
• The 87th Amendment Act, 2003 replaced the 1991 Census with the 2001 Census as the basis for this permitted readjustment of constituencies and reserved seats.

Resulting framework

The amendments separated seat allocation from boundary delimitation. Inter-state Lok Sabha allocation and state assembly strengths remain tied to the 1971-based arrangement, while present constituency boundaries were readjusted using 2001 population figures; a fresh allocation is not triggered merely by reaching 2026, because publication of the relevant post-2026 census figures is required.