Why can a party win more votes but fewer seats?

Under First Past the Post, votes do not translate directly into Commons seats according to national vote share.

The system asks a different question:

Who came first in each of the 650 constituencies?

That means a party can receive more votes nationwide than another party and still win fewer MPs.

A simple example

Imagine a country with three constituencies.

Constituency 1

Party A: 60,000
Party B: 40,000

Party A wins.

Constituency 2

Party A: 20,000
Party B: 21,000

Party B wins.

Constituency 3

Party A: 20,000
Party B: 21,000

Party B wins.

Now add the votes.

Party A: 100,000 votes

Party B: 82,000 votes

Yet Party B wins 2 seats and Party A wins 1 seat.

Party A received more votes overall but fewer MPs.

Why does that happen?

Party A's extra 20,000-vote lead in Constituency 1 does not create additional seats.

Once Party A has finished first there, a larger majority does not increase its Parliamentary representation.

Party B's votes are more efficiently distributed for winning this particular set of constituencies.

What does "vote efficiency" mean?

It is an informal way of describing how effectively a party's votes are distributed for winning seats.

A party can be disadvantaged if it:

• piles up very large majorities in seats it already wins;
• finishes second by small or medium margins in many other constituencies.

A party can be advantaged if it:

• wins many seats narrowly;
• has fewer votes concentrated in constituencies where they make no difference to the winner.

This is not something fixed permanently to particular parties.

The geography of party support changes between elections.

A real example from 2024

House of Commons Library analysis of the 2024 general election shows the effect clearly.

Reform UK received approximately 14.3% of votes but around 0.8% of Commons seats.

The Liberal Democrats received approximately 12.2% of votes but around 11.1% of seats.

The Liberal Democrats therefore won substantially more MPs despite receiving a smaller national vote share.

The reason was not that one party's ballots counted for more.

Every constituency was counted under the same FPTP rule.

The difference arose from where the votes were cast and which candidates finished first.

Does this mean FPTP always helps large parties?

Not in a simple universal way.

FPTP has often benefited parties whose support is geographically efficient, and it can produce large seat bonuses for the leading parties.

But outcomes depend on:

• concentration of support;
• number of competitive parties;
• constituency boundaries;
• tactical voting;
• regional political patterns;
• size of winning and losing margins.

A smaller party with highly concentrated regional support can sometimes win many seats from a modest UK-wide vote share.

A party with broadly spread but shallow support can win few.

What is disproportionality?

An election result is described as disproportionate when the share of seats differs substantially from the share of votes.

FPTP does not aim to make national seat share proportional to national vote share.

Its basic unit is the single-member constituency.

Arguments about whether that is desirable belong to the wider debate about electoral systems.

Would proportional representation make votes and seats match exactly?

Not necessarily exactly.

Different proportional systems use different:

• formulas;
• electoral regions;
• thresholds;
• constituency structures;
• methods of allocating seats.

But proportional systems are generally designed to make overall representation more closely reflect vote shares than FPTP.

The Road to Number 10 simulation includes an alternative-electoral-system comparison so users can see how the same simulated votes might translate differently under different rules.

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