Executive summary

Following each general election for the House of Representatives, the Australian Electoral Commission (AEC) undertakes an Informal Ballot Paper Study (IBPS) to analyse the levels and types of informal voting. Research based on the IBPS is fundamental to the AEC’s role in supporting electoral integrity by:

• Informing education and information strategies to reduce informal voting, including through the provision of robust information at the polling place level.
• Providing an evidence base for reforms to the electoral system, for example, by enabling analysis of the impact of Optional Preferential Voting, and aligning savings provisions between the House of Representatives and the Senate.

The national informality rate (informal votes as a percentage of all votes cast) decreased from 5.91 per cent of all votes cast at the 2013 House of Representatives elections to 5.05 per cent at the 2016 House of Representatives elections.

At the state and territory level, the highest informality rates for the 2016 House of Representatives elections were in the Northern Territory, New South Wales and Victoria, while the lowest informality rates were in the Australian Capital Territory, Tasmania and Western Australia.