THE Additional Member voting system used to elect the Scottish Parliament is sometimes characterised as a “semi-proportional” system, implying that only the 56 list seats are elected proportionally. That’s highly misleading, because the basic idea behind the system is that the overall result should be roughly proportional to how people voted on the list ballot, with list seats being distributed “correctively” to achieve that aim. If, say, a party wins 25 per cent of the list vote but takes hardly any constituency seats, the system should award it a disproportionately high number of list seats to ensure that it’s left with roughly one quarter of the 129 seats in parliament.

That’s the theory, but the version of the Additional Member system we use in Scotland doesn’t work quite as efficiently in practice.

Labour were in the driving seat when the details of the system were decided in the late 1990s and, unsurprisingly, were keen to retain some form of artificial bonus from their traditional strength in constituency seats. This was achieved in three ways. Firstly, there were fewer list seats (56) than constituency seats (73), making it harder for an extreme imbalance in constituency seats to be reversed. In some circumstances a party might even reach the target for an overall majority (65) before a single list vote was even taken into account. Secondly, list seats were distributed on a regional rather than national basis, making it even less likely that Labour’s total dominance of constituency seats in west-central Scotland could be corrected for. Thirdly, the possibility of extra list seats being awarded when that was necessary to achieve a proportional outcome was ruled out.

The net result was that Labour won 43 per cent of the seats in 1999 when its list vote should have entitled it to only around 34 per cent. That was only the first in a series of Holyrood election outcomes that people have found perverse in some way, which culminated last year in the SNP losing their overall majority in spite of their constituency vote increasing to an all-time high of 46.5 per cent. That happened after a campaign that sought to convince voters that the SNP could win on constituency seats alone, and therefore didn’t “need” list votes.

For some time now, Alex Salmond has been proposing a potential solution to at least some of these problems. He suggests that the confusion over the importance of the list ballot should be addressed by having just one allpurpose ballot, which would elect both constituency and list MSPs. He also wants the regional list system to be replaced by a single national list.

It’s just conceivable, though, that this idea might have led to a less favourable outcome from a proindependence point of view had it been used in last year’s Holyrood election. The 59 constituency seats won by the SNP constitute less than 46 per cent of the overall seats in parliament, leaving just enough scope for a national list to bring the party down to the roughly 47 per cent of seats they would have been entitled to. That’s assuming people would have voted exactly as they did on the constituency ballot, in which case there would actually be a Unionist majority. If they instead would have voted more in line with the list result, there would be a pro-independence majority, but the SNP would be even further away from a majority of their own.

If Salmond is looking for a system that removes the confusion of the list ballot while still offering a realistic possibility of an overall SNP majority, he’d be better advised to embrace the Single Transferable Vote system we will soon use for the local elections. It’s long been regarded as the Holy Grail by LibDems, and is also supported by the Greens.

That’s important, because a two-thirds majority in the Parliament is required before any overhaul can take place.