D'Hondt system for picking NI ministers in Stormont

D'Hondt formula on whiteboard

It is named after its creator, 19th century Belgian lawyer and mathematician Victor D'Hondt

Government departments in Northern Ireland are allocated using the obscure-sounding D'Hondt mechanism, but what does this entail?

There are 12 departments in the Northern Ireland Executive, which operates as a coalition.

These need to be shared out among the parties who gained the most seats in the assembly election, and the D'Hondt mechanism is used to calculate who gets what.

The Good Friday Agreement stipulated that the D'Hondt system should be used to share out Stormont ministries between the parties, as it was felt to be suitable for use in a divided society, aimed at ensuring cross-community representation.

'Highest average'

It uses a mathematical formula which involves the principle of "highest average".

This means it tends to favour larger parties: the idea is that it reflects the strength of a party's total support by taking into account the number of seats it won in the election.

Departments are assigned one at a time, beginning with the party with the highest total.

As the largest party, the DUP has the first choice of ministry, followed by Sinn Fein, the second largest party, and so on.

The system differs from the single transferable vote (STV) in that it does not use a quota or formula to allocate seats or posts.

Rather, these are allocated singularly and one after another.

  • A party's total vote is divided by a certain figure, which increases as it wins more seats;

  • As that dividing figure increases, the party's total in succeeding rounds gets smaller - this allows parties with lower initial totals to win seats;

  • In the first round of vote-counting, the dividing figure is one and therefore has no effect;

  • However, the figure in subsequent rounds is the total number of seats gained plus one.

Also under D'Hondt, the parties nominate committee chairs and committee members of the assembly.

A party can exclude itself from the executive committee, and if it withdraws its support for the committee its seats can be re-distributed under D'Hondt.