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Relevance: GS-I (Population); GS-II (Governance); GS-III (Internal Security & Border Management) Source: Census Data / Demographic Studies, 2026

1 · What is the debate all about?

We often hear a popular narrative in political discussions: “There are roughly 20 million (2 crore) illegal Bangladeshi migrants residing in India.”

But as UPSC aspirants, let us look past the political noise and analyze the hard scientific facts! If 2 crore undocumented migrants actually live in India, they would inevitably leave a footprint during our decennial Census. Recent demographic studies comparing official Census figures with Post Enumeration Surveys (PES) mathematically put this massive claim to the test.

2 · A Migrant’s Three Choices During a Census

When a Census enumerator knocks on the door, an undocumented migrant can react in only three ways. Let us see how official data refutes all three scenarios for the claimed 2 crore figure:

Scenario 1: Ducking (Hiding)
Could they be hiding?
If millions hid, we would see massive omission errors. However, the Post Enumeration Survey shows our Eastern border zone had an omission rate of just 0.84% (only 22 lakh people missed). You mathematically cannot hide 2 crore people there!
Scenario 2: Misreporting
Could they lie about birthplace?
If millions faked being Indian, we would see abnormal, unexplained population spikes along border districts. But demographic analyses show normal, steady growth that matches local fertility rates. No secret spike exists.
Scenario 3: Truthful Response
What if they told the truth?
The Census counts “migrant stock” purely by birthplace. Official records show Bangladeshi-born individuals in India actually dropped by one-third, falling from 40 lakh in 1991 to just 27 lakh in 2011!
The Aging Reality
An Elderly Population
Why are the numbers dropping? Because 43.65% of these migrants are senior citizens (60+ years old). They arrived decades ago during the 1947 Partition or 1971 war, and their numbers are falling naturally as that generation passes away.

  • The Bottom Line: While it is impossible to say there are zero illegal migrants, official scientific data proves that a hidden population of 20 million simply does not exist. Internal security policies must be built on empirical facts, not exaggerated political estimates.

UPSC Prelims Quick Facts
ORGI Office of the Registrar General & Census Commissioner, India. Functions under the Ministry of Home Affairs (MHA) and conducts the Census under the Census Act, 1948.
PES Post Enumeration Survey. An independent sample survey conducted right after a Census to measure coverage errors (missed people) and content errors (wrong details).
Demographic Migrant Stock In Census terms, anyone born outside India is automatically counted as a “migrant” based on geography, regardless of whether they have a legal visa.
Legal vs. Illegal Migrant Under the Citizenship Act, 1955 and Foreigners Act, 1946, legality is defined strictly by the possession of valid travel documents or visas, not just birthplace.

MCQ Practice Question
Q. With reference to the Census methodology and migration frameworks in India, consider the following statements:

  1. The Post Enumeration Survey (PES) is conducted by the Ministry of Statistics and Programme Implementation to verify GDP growth numbers.
  2. In the Indian Census, the determination of ‘migrant stock’ is based purely on a person’s place of birth or place of last residence, irrespective of their legal citizenship status.
  3. The decennial Census of India is conducted under the statutory provisions of the Census Act, 1948.

Which of the statements given above is/are correct?
(a) 1 and 2 only    (b) 2 and 3 only    (c) 1 and 3 only    (d) 1, 2 and 3

Answer: (b) 2 and 3 only

  • Statement 1 — Incorrect: The Post Enumeration Survey (PES) is conducted by the Office of the Registrar General & Census Commissioner (under the Ministry of Home Affairs) specifically to measure coverage and content errors in the Census, not GDP.
  • Statement 2 — Correct: The Census is a demographic exercise; it counts “migrants” purely based on geographical origin (place of birth/last residence), without checking travel documents or citizenship.
  • Statement 3 — Correct: The ORGI derives its statutory authority to conduct the population census from the Census Act of 1948.
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