By Bhanu Joshi  & Neelanjan Sircar

From November to February, more than nine million names were deleted from the Bengal electoral rolls in the space as part of what the Election Commission of India calls a Special Intensive Revision.

This was followed by a shock landslide win by the Bharatiya Janata Party on May 4, where the Hindutva party won 70% of the seats in the Assembly.

In this piece, we use statistical methods to examine whether SIR deletions were associated with electoral outcomes. We also build a simple model to try and quantify the extent of the impact.

Our analysis shows a strong relationship between SIR deletions and electoral performance in Bengal: constituencies where the electoral roll shrank more also saw the BJP do better relative to its main challenger, the Trinamool Congress. Notably, a comparable exercise in Bihar, which also underwent an SIR, shows no equivalent pro-ruling alliance pattern linked to roll shrinkage.

Our method

We seek to find the relationship between voters deleted during the SIR and the relative performance of the BJP and Trinamool: the two main players in this election.

This approach differs from much of the existing discussion, which compares the number of deleted voters with the final winning margin. In our view, that arithmetic misses how rolls actually shape elections. Roll deletion does not merely subtract names from a list. It can change the composition of the electorate that remains, the balance of local coalitions and the signals voters and parties read about who is strong.

The better test, then, is whether roll shrinkage was systematically associated with changes in party margins.

To do this, we must understand the relationship between roll shrinkage and the relative electoral performance of the BJP vis a vis the Trinamool, using Assembly constituency level data.

In West Bengal, “all-cause” roll shrinkage is measured as the percentage fall in total electors from the 2024 Lok Sabha divided by assembly segments to the final post-SIR roll before the 2026 Assembly election. For example, in Kolkata’s Bhabanipur assembly constituency, the number of electors shrank from 2,05,553 in the 2024 general election to 1,60,313 in the final post-SIR roll before the 2026 election – a roll shrinkage of 22%.

This story was originally published in scroll.in. Read the full story here.