The existing Scottish Parliament system is also known as the D’Hondt system, named after a Belgian lawyer from the 1870s.
Unlike the single transferable vote, it does not use a quota or formula to allocate seats or posts. The basic idea is that a party’s vote total is divided by a certain figure which increases as it wins more seats. This slightly favours large parties and coalitions over scattered small parties.
Other legislatures that use this system include Belgium, Brazil, Israel and Spain, as well as Northern Ireland and Wales.
National proportional representation (1)
Under this system, there would be only one Scotland-wide area for list MSPs, with an end to regions such as South of Scotland and the North East. Constituencies would carry on as before.
The idea is that by having one big Scottish region for list MSPs, the result would be more proportional than with lots of different regions, as at present.
This example includes a threshold of 5 per cent of list votes to win a seat – that is the system used in Germany.
National proportional representation (2)
This would operate on same basis as the other system of national PR, using one Scotland-wide regional list, but with a lower threshold of 4 per cent.
This means smaller parties would be more likely to win a greater number of seats in the Scottish Parliament.
This complex system, named after the French mathematician André Sainte-Laguë, is one way of allocating seats approximately proportional to the number of votes cast for list candidates.
This system is used in New Zealand, Norway, Sweden, Bosnia and Herzegovina, Latvia, Kosovo, Denmark and part of Germany.
It is quite similar to the D’Hondt method but uses different divisors, so favouring smaller parties.