Rates of ‘Below the Line’ Voting at the 2017 WA Legislative Council Election

This is a post for those who want to follow the output from the ABC’s Legislative Council election calculator once its starts running with live result data.

The calculator assumes that all votes cast are ticket or ‘above the line’ (ATL) votes. In close contests, the relatively small number of below the line (BTL) votes may impact on the prediction by causing a drift away from the party’s preference ticket.

For anyone interested in assessing the accuracy of calculator predictions, this post contains relevant data from 2017 on the rates of BTL voting by party, vote type and region.

In summary, the 2017 data indicates that the rate of BTL voting has little relationship to the region in which a vote is cast, or the type of vote (postal, pre-poll etc) used by a voter.

Where real differences occurs is in the relationship between a voter’s first preference party choice and the likelihood of choosing to cast a BTL vote.

The rates of BTL voting are lowest for the major parties, at 2.9% for the Liberal and Labor parties, a higher 5.6% for the National Party.

The lowest rate of BTL voting for any party was 2.2% for the Liberal Democrats.

Of the larger parties, the Greens stand out with 11.7% of all Green votes being completed below the line.

Apart from the Greens, there is a general pattern that rates of BTL voting are inversely related to a party’s percentage of first preference vote. The higher a party’s first preference vote, the lower the rate of BTL voting, and the lower a party’s rate of first preference vote, the higher the rate of BTL voting.

Note that the high rate shown for Independents is the accumulation of votes for many low polling Independents. There has also been some evidence at recent Senate elections that voters are more likely to vote below the line in ballot paper columns with no party label above the line.

Table 1 – Rates of ATL and BTL Voting by Party – 2017 WA Legislative Council Election

Vote Type % of
Formal Vote
% ATL Vote % BTL Vote
Labor Party 40.41 97.1 2.9
Liberal Party 26.71 97.1 2.9
Greens 8.60 88.3 11.7
One Nation 8.19 95.1 4.9
National Party 4.43 94.4 5.6
Shooters Fishers Farmers 2.37 93.9 6.1
Australian Christians 1.94 91.9 8.1
Liberal Democrats 1.77 97.8 2.2
Independents 1.15 82.6 17.4
Animal Justice Party 1.10 93.1 6.9
Family First 0.84 95.1 4.9
Daylight Saving Party 0.68 91.9 8.1
Micro Business Party 0.55 90.3 9.7
Flux the System! 0.44 83.6 16.4
Julie Matheson for WA 0.39 86.4 13.6
Fluoride Free WA 0.32 90.0 10.0
Socialist Alliance 0.10 76.4 23.6
Total 100.0 95.4 4.6

Table 2 shows the rate of ATL and BTL voting by vote type and reveals very little difference by type. The rate of BTL voting on polling day in district was 4.5%, polling day Absent 4.2%, Pre-poll 4.1% and the highest rate 6.5% for postal votes. The lowest rate was 1.1% with mobile voting collected mainly in nursing homes and in remote indigenous communities.

If you look at the rate of BTL voting by vote type cross tabulated with first preference vote by party, it is clear that the causal variable in tendency to use BTL voting is related to who a voters chooses as their first preference party, not the type of vote cast.

Table 2 – Rates of ATL and BTL Voting by Vote Type – 2017 WA Legislative Council Election

Vote Type % of
Formal Vote
% ATL Vote % BTL Vote
Polling Day 63.3 95.5 4.5
Pre-Poll 16.2 95.9 4.1
Absent 11.2 95.8 4.2
Postal 8.6 93.5 6.5
Mobile 0.7 98.9 1.1
Provisional 0.1 97.8 2.2
Total 100.0 95.4 4.6

Table 3 simply demonstrates there was little difference in rates of BTL voting by region at the 2017 election. Again, looking at cross tabulation of region with first preference votes shows that first preference vote is most strongly correlated with, if not responsible for, a tendency for voters to cast a BTL vote.

Table 3 -Rates of ATL and BTL Voting by Region – 2017 WA Legislative Council Election

Region % ATL Vote % BTL Vote
East Metropolitan 95.4 4.6
North Metropolitan 94.6 5.4
South Metropolitan 96.1 3.9
Agricultural 95.3 4.7
Mining and Pastoral 96.3 3.7
South West 95.5 4.5
Total 95.4 4.6