Seat share vs vote share: Congress’s victory maths in Himachal
While the Congress’s seat share to vote share ratio has increased significantly from 0.74 to 1.34 between 2017 and 2022, the BJP’s has fallen sharply from 1.33 to 0.85.
With 40 legislators in the new assembly, the Congress has won a simple majority in the 68-member Himachal Pradesh assembly. The Bharatiya Janata Party (BJP), which won 44 seats in the previous assembly, has finished second with 25 MLAs. What is interesting about the Himachal Pradesh results is the fact that the seat share difference between the Congress and the BJP is significantly larger than the vote share difference of just 0.9 percentage points. What explains this fact?
Looking at the seat share to vote share ratio of the two main parties in the state is a good place to start this discussion. Seat share to vote share ratio is among the simplest, yet most effective, metrics to compare a party’s ability to convert popular support into seats in a first-past-the-post system.
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While the Congress’s seat share to vote share ratio has increased significantly from 0.74 to 1.34 between 2017 and 2022, the BJP’s has fallen sharply from 1.33 to 0.85 . To be sure, it is neither the highest for the Congress nor the lowest for the BJP if one compares the data from 1982, the earliest period which data is available for both the Congress and the BJP.
One reason that could explain the Congress’s higher seat share to vote share ratio in these elections is the fact that its performance has been more even through the state than it was in 2017.
This can be seen from the fact that the median vote share of the Congress (47.3%) is significantly higher than that of the BJP (44.2%) compared to the difference between the overall vote share of the two parties in the state. In fact, 2022 has seen the Congress’s best median vote share performance since 1998. This basically means that the BJP’s overall vote share has been driven by very good performances in a handful of assembly constituencies while the Congress’s performance has been more consistent throughout the state. This is best shown by looking at the difference in vote shares of the Congress and the BJP at the AC-level. While the BJP has a deficit of just two ACs vis-à-vis the Congress in ACs where the vote share difference between the two parties is more than 15%, its deficit increases to seven in ACs where the vote share difference between the two parties is less than 5%.
Could other parties or independents cutting into the BJP’s votes also be a reason for the Congress’s high seat share to vote share ratio? Data shows that this is not the case in 2022. The Congress has lost 13 ACs to parties playing spoiler while the BJP has lost 12 ACs, with Independent candidates playing spoiler in nine ACs for each party, and the Aam Aadmi Party in one AC each.
A party is said to have played spoiler here if it finishes third, but has vote share greater than the victory margin.