This is part of a three-part series on the UK’s usage of Alternative Vote. For Part 1, see here. For Part 3, see here.

On May 5th, 2011, the UK held a referendum on adopting the Alternative Vote system, or otherwise known as Instant-runoff voting (IRV). Supported by the Liberal Democratic party as part of a coalition agreement with the Conservatives, the referendum ended in a decisive loss for those advocating for a change.

In the second part of this series, we analyse the results of the 2010 UK election if it had be conducted under Alternative Vote, as suggested by the Liberal Democrats.

UK-AV

The Liberal Democrats lose slightly in this model – it seems that the reform of the electoral system to an AV system would not have really improved their fortunes. This is because The district magnitude (number of candidates elected per district) in AV is still one – which means that a nation still tends towards a two-party system.

The biggest impact from this simulation is the almost-complete exclusion of the pro-independence parties. This could be due to the fact that they are rarely ever the second choice of any voter – in almost all cases a voter would end up having his or her votes redistributed among other unionist parties. Once a critical point is reached, such as in the case of 2015, an wide gain for independence parties can be expected.

All-in-all, it seems that the adoption of an AV system would not have led to that large of an improvement for the Liberal Democrats. Instead, the effect has been more varied, benefiting Labor more in this instance and not leading to any clear change.

With data from 2015 and 2010, along with other data and simulations, we can analyse how AV could have changed history.

Appendix

We largly retain the same assumptions used in Part 1. We assume that Fir