Explanation: The 42nd Amendment Act of 1976 froze the allocation of seats in the Lok Sabha to the states and the division of each state into territorial constituencies till the year 2000 at the 1971 level.

• This ban on readjustment was extended for another 25 years (ie, up to the year 2026) by the 84th Amendment Act of 2001, with the same objective of encouraging population limiting measures.
• The 84th Amendment Act of 2001 also empowered the government to undertake readjustment and rationalization of territorial constituencies in the states on the basis of the population figures of 1991 census.
• Later, the 87th Amendment Act of 2003 provided for the delimitation of constituencies on the basis of 2001 census and not 1991 census.
• However, this can be done without altering the number of seats allotted to each state in the Lok Sabha.

Source: Laxmikanth