Scotland's May Elections

The Scottish Parliament’s electoral system is infamously complex. More than two decades after it was introduced, its effects are poorly-understood by voters and politicians alike.

Ahead of May’s Scottish elections, two parallel parties have sprung up -- Alba on the Nationalist side and Alliance for Unity (A4U) on the Unionist side -- both claiming to maximize their side’s share of Holyrood seats by more efficiently allocating regional list votes.

Despite similar messages, Alba and A4U have vastly different chances of electoral success

While both parties make plausible arguments, Stack modelling demonstrates that Alba is much better positioned to succeed electorally, while A4U is most likely to inadvertently harm the Unionist cause. This disparity is largely due to the fact that, at current support levels, the Unionist side currently depends much more heavily on list seats than the Nationalist side.

The Scottish Electoral System

Voters in Scottish elections each receive two votes: a constituency vote and a regional list vote. 73 out of Holyrood’s 129 seats are allocated using the constituency vote, through a first-past-the-post system similar to UK-wide general elections. In each constituency, the party with the most votes wins and is assigned an MSP.

The regional list vote is intended to correct for the imbalances that first-past-the-post introduces by allocating the 59 remaining Holyrood seats through a system that handicaps parties which have already won constituency seats. Specifically, Scotland uses a modified version of the d’Hondt system for this allocation.

In each of Scotland’s eight regions, the regional list votes for each party are tallied up and then divided by the number of constituencies which each party won in the region, plus one, to give a d’Hondt ‘quotient’. The party with the highest d’Hondt quotient in the region is allocated one MSP, and then the same calculation is repeated but with one added to the divisor of the party that was just allocated an MSP, meaning its d’Hondt quotient is lowered. This process continues until all MSPs in the region have been allocated.

Parties typically need around 6 to 7 percent of list votes to win at least one MSP through this system. If their vote is any lower, their d’Hondt quotient will never be high enough, even as the d’Hondt quotients of other parties are lowered when they are assigned MSPs. Any votes for a party that falls below this 6-7 percent threshold are effectively wasted.‍

The Regional List Loophole

This system also has an important vulnerability: the handicap that lowers the d’Hondt quotients of parties which have already won constituency seats does not apply to parties which are technically separate, but in practice stand on nearly identical platforms. Hence, both Alba and A4U, neither of which are campaigning for constituency votes, don’t suffer any d’Hondt penalty, even if allied parties win heavily in the constituency vote.

Because the Nationalist vote is concentrated behind the SNP, while the Unionist vote is divided between several large parties, the Nationalist bloc typically wins most constituency seats, but very few list seats. In 2016, the SNP won 59 constituency seats, but just 4 list seats (though the pro-Independence Scottish Greens won another 6 list seats). As a result, the Nationalist side has much more to gain by gaming the regional list system -- almost all SNP votes re-allocated to Alba would otherwise have been ‘wasted’. Conversely, most Unionist seats are won through the regional list, meaning that even if it is successful, A4U is likely to simply displace other Unionist MSPs, rather than net adding to the size of the Unionist bloc in Holyrood.

Stack has modelled the Scottish electoral system to test these assumptions. We calibrated this model using the Panelbase/Sunday Times poll published on March 4th, and worked under the assumption that all potential Alba votes would be direct transfers from the SNP and all potential A4U votes would come from other Unionist parties.

Our results verified this theory; Alba would ‘take off’, and become a major net benefit to the Nationalist side at around 6%, a level they have already reached in some recent polling. But for A4U, that threshold is over 30%, meaning A4U would need to win the clear majority of all Unionist votes cast before it stops being a hindrance to the Unionist cause.

The UK has a long history of political movements that failed to adapt properly to the electoral systems they face, Change UK being just the most recent example. As a crucial Holyrood election approaches, it is vital that voters on all sides are well informed about which parties are electorally viable, which could change the country’s future, and which will simply lead to a wasted vote.

Stack’s analysis was originally published in The Spectator. The article can be found here.