Delimitation is a statutory concept and an act that involves fixing the number of seats and redrawing the boundaries of territorial constituencies for the Lok Sabha and State Legislative Assemblies in India. The process is mandated to ensure that each constituency represents a roughly equal population, thereby upholding the principle of "One Vote One Value". The origin of the formal process lies in the post-independence era, with the first Delimitation Commission constituted in 1952 under the Delimitation Commission Act, 1952, to address the problem of unequal representation following population changes.
The mechanism is governed by Article 82 of the Constitution, which mandates Parliament to enact a Delimitation Act after every Census, and Article 170, which governs the division of State Legislative Assembly constituencies. The task is assigned to the Delimitation Commission, a high-powered, quasi-judicial body appointed by the President of India, whose orders have the force of law and cannot be challenged in any court under Article 329(a). The Commission also determines the seats to be reserved for Scheduled Castes (SCs) and Scheduled Tribes (STs) as per Articles 330 and 332.
The process has been significantly altered by constitutional amendments: the 42nd Amendment Act of 1976 froze the allocation of seats in the Lok Sabha and State Assemblies based on the 1971 Census figures to avoid penalizing states that successfully implemented family planning programs. This freeze on the total number of seats was extended until the "first census conducted after the year 2026" by the 84th Amendment Act of 2001. The last full delimitation exercise was conducted by the Commission set up in 2002 under the Delimitation Act, 2002, but it only readjusted constituency boundaries within states based on the 2001 Census population, without changing the total number of seats allocated to each state. The next major delimitation, which will involve inter-state seat redistribution, is expected after the census following 2026.