Bonus Seats Calculation

Under our Proportional Representation Single Transferable Vote system a party should get an equal share of seats to votes. In other words if a party gets 20% of the first-preference vote they should get 20% of the seats.

This would give a % Seats to % Votes Ratio of 100%. But the aim is to do better than this, writes Political Analyst Sean Donnelly.

I have used this seats to votes ratio as a Performance Indicator (PI) for the various parties.

General Election 2011

The table below shows the bonus seats achieved in 2011 and the PI.

There were 21 bonus seats in play in 2011 mainly because of the collapse in the Fianna Fáil vote. Fine Gael did extremely well on bonus seats as they won 16 seats more than their first-preference vote would have warranted and this was the difference between a reasonably good election with 60 seats to getting close to an overall majority at 76 seats.

This resulted in a seats to votes ratio of 128%, the best achieved by any party since the first PR-STV election in 1922. Fianna Fáil were the big losers and instead of getting at least 29 seats they got nine less and for the first time got less seats share than votes with a PI of just 69%.

Sinn Féin have never got a seats bonus and were three adrift in 2011 for a ratio of 85%. Labour pushed their ratio up to 115% from their average of 104% with the others on a negative bonus at just 67%.

Local Election 2014

Fine Gael had a poor Local Elections in 2014 and were overtaken by Fianna Fáil who became the biggest party with 20 more bonus seats.

Fine Gael had a small bonus with a ratio of just 103%. Fianna Fáil were close to their average with 111%. Sinn Féin broke the mould and got a seats bonus for the first time winning 110%.

Labour had a very poor local election and this was reflected in their Seats to Votes ratio as they got just 75%, their worst since 1944.

Others were again below the bench mark at 76% but this was an improvement on 2011 when they got 67%.

General Election 2016

Fine Gael had a poor election in 2016 but were saved by their vote management. They were just one point ahead of Fianna Fáil on first preferences which would have given them just a one seat advantage but a better bonus seats performance saw them winning twice as many bonus seats to edge the gap to six seats.

Thus Fine Gael went close to their excellent 2011 performance with a ratio of 124%, their second best ever.

Fianna Fáil also did well and were above their historical average and above their 2014 locals ratio. But good vote management gave Fine Gael two seats or more in 15 constituencies with Fianna Fáil winning two in just nine and that was the main difference between the two largest parties.  

Sinn Féin got one bonus seat for a positive ratio of 105%, which was down on their local election ratio of 110%.

The Others as expected fell well short of what their first preference vote warranted as they took 13 seats less for a ratio of just 67%, down from 89% in the locals. 

None of the smaller parties came up to scratch and were all below the 100% bench mark from AAA-PBP best at 96% to The Green Party at just 47% (excluding Renua).

First Past the Post v PR-STV

We may complain about our electoral system but at least it is reasonably fair, especially when it is compared to our near neighbours in the UK.

The 2015 general election in the UK dramatically showed how un-democratic the first-past-the-post system is. 

It ranges from the SNP winning nearly twice the number of seats compared to their share of the vote with UKIP at the other end of the scale, winning just one seat from 13% of the vote.

Only the Labour Party fell within our range with a Seats to Votes ratio of 117%.