Proportional Representation - How it works

A total of 1,178,583 people are entitled to vote in Northern Ireland's Assembly elections tomorrow. This is almost 3,000 more than in last month's referendum on the Belfast Agreement, in which the 71.1 per cent Yes vote paved the way for the Assembly.

Each of the 1,228 polling stations opens at 7 a.m., and voting will continue until 10 p.m. Counting begins in all 18 constituencies at 9 a.m. on Friday, with an average of 45 counting staff in each count centre. All the Belfast counts will take place at the City Hall, and the remainder in eight regional centres.

There is no time limit for completion of the counts, but at about teatime on Friday local returning officers will decide whether to suspend the counting operation for the night or continue.

The chief electoral officer, Mr Pat Bradley, said yesterday that where there was a reasonable prospect of reaching a declaration on Friday night the counts might continue without interruption. But at least some may have to resume on Saturday.

The possibility of counting on Sunday is not being considered at the moment, but it appears unlikely. In Northern Ireland, Sunday is generally held to be a day of rest.

The 18 constituencies average about 66,000 voters each and will elect 108 representatives, six per constituency. This means one Assembly member for every 11,000 voters. In the Republic, about 2.7 million voters elect 166 TDs to the Dail, more than 16,000 electors for each TD.

When the Assembly election was being planned, the smaller political parties wanted a "top-up" system whereby a small number of seats would be set aside and shared among the top 10 parties by votes gained overall.

This was not agreed at the multi-party talks which led to the adoption of the Belfast Agreement. Instead, an election offering six seats in each constituency was proposed. The larger parties said that six-seater constituencies would ensure adequate representation for smaller groups, although the small parties were dissatisfied with this.

The highest number of candidates in any constituency is Strangford's 22. East Belfast has 20 while, at the other end of the spectrum, Mid-Ulster has only 13. There are 296 candidates overall.

Proportional representation voting is not new to Northern Ireland: it is used in European and local elections. Only in Westminster elections is the first-past-the-post system used.