What is delimitation? 

The demarcation of the boundaries of parliamentary or assembly constituencies is known as delimitation. The process is carried out every few years to ensure that each constituency has approximately an equal number of voters. Therefore, the exercise is carried out after every Census.
After every Census, Parliament enacts a Delimitation Act under Article 82 of the Constitution. Subsequently, a high-powered body known as the Delimitation Commission is constituted, which carries out the process of demarcation of constituency boundaries.
The orders of this commission are legally binding and not subject to scrutiny under any court of law. In fact, even Parliament cannot suggest modifications to an order issued by the commission.
The commission consists of a chairman — a retired or sitting judge of the Supreme Court, the Chief Election Commissioner or any of the two election commissioners, and the election commissioner of the state in which the exercise is being carried out. In addition, five MPs and five MLAs of the state are chosen as associate members of the commission.
Since the commission is a temporary body with no full-fledged staff of its own, it relies on EC staff to carry out the long-drawn-out exercise. Census data for each district, tehsil and gram panchayat is collected, and the new boundaries are demarcated. The exercise can take up to five years to be concluded for the whole country.
When has it happened before?
A Delimitation Commission was first constituted in 1952. Subsequently, they have been constituted in 1963, 1973 and 2002. However, in 2002, the Constitution was specifically amended not to have delimitation of constituencies until 2026.
The guiding logic behind this was that by 2026, the population growth across states would be somewhat similar. Otherwise, states which performed poorly in terms of population control would be rewarded by increasing their constituency tally, and those which took measures to control their population would have fewer
constituencies.
Delimitation and 84th Amendment Act 200
Delimitation and 84th Amendment Act 2002
Delimitation and 84th Amendment Act 2002
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Delimitation and 84th Amendment Act