The assembly will consist of 60 members.

They will be known as Members of the Welsh Assembly, or MWAs, and will be chosen in one of two ways:

• 40 members representing individual constituencies and elected under the traditional First Past The Post system.

  These will be the same as the 40 Welsh constituencies at Westminster.

• 20 members selected from 'party lists' in the country's five electoral regions.

  These regions are the same as the current European parliamentary boundaries and each will elect four MWAs through the Additional Member System, a form of proportional representation.

Electors will therefore have two votes on separate ballot papers. One for a candidate in their constituency (mauve ballot paper) and one for a party list in their region (peach ballot paper). Voters will also be given a white ballot paper, but this is for the separate Welsh local council elections.

Dispelling confusion

Independent research has found two main ways that people are confused by the new system:

• Some people mistakenly believe that they must vote for the constituency candidate belonging to the same party they supported at regional level.

• Other people mistakenly believe the opposite, that the regional vote is a 'second choice' and that they must therefore vote for a different party to the one they voted for in their constituency.

It is up to individual voters to decide whether or not they 'split' their votes.

They can vote for the candidate at constituency level who represents the same party or a different party to the one they voted for at regional level.

The Additional Member System

The constituency MWAs are chosen according to the traditional system used in Westminster elections. A candidate needs simply to poll more votes than any other single rival to be elected.

The system for electing the Additional Members is more complex.

Electors will cast their second vote for a 'party list'. This is a list submitted by registered parties with their list of candidates in order of preference.

If the party succeeds in winning a one of these 'top-up' seats, the person named as first on its list will be elected. If it wins two top-up seats, then the first two will be elected, and so on.

It is important, therefore, for candidates to be near the top of their party's list for them to stand a realistic chance of being elected.

There are two complications to the lists.

First, a 'party list' can be an individual person who is standing at the regional level rather than in a constituency.

Secondly, several candidates are standing both in a constituency and on a regional top-up list. If they succeed in a constituency this takes priority and their name will be removed from the regional list so they cannot be elected twice.

The all-important divisor

The formula for deciding which parties win regional top-up seats is known as the d'Hondt system and is used widely across Europe.

It is also used in the Northern Ireland Assembly to allocate positions on the executive.

First, party list votes are totalled from each of the constituencies making up the region.

These totals are then divided by the number of constituency seats each party has won - plus one.

The party with the highest resulting total elects one Additional Member. That party's divisor is then increased by one (because of its victory) and new figures calculated. Again, the party with the highest resulting total wins a seat.

The process is then repeated until all Additional Members are elected.

The aim of the system is to compensate parties which pile up lots votes in constituencies but fail to win many MWAs. Under the d'Hondt system, they are much more likely to gain Additional Members. Conversely, parties which do well in constituency elections will do less well in the top-up seats.

Click here for a demonstration of how this system works in practice.