One of the original stated reasons for introducing group voting tickets to Senate elections was to reduce the high incidence of informal voting, around 10% at the time. By requiring voters to only mark one preference above the line, informal voting did indeed decline. However, an alternative way to reduce the number of informal votes is to not require all preferences to be marked, as suggested in Section 3.2.2. Allowing the number of preferences to be as low as the district magnitude (partial preferential), or even a single preference (optional preferential) would reduce the incidence of informal voting without introducing the distorting influence of group voting tickets.
In 1948, when proportional representation was introduced for Senate elections, there was significant debate over the stringent formality requirements proposed, and the problem of high numbers of informal votes was foreseen. Dr Evatt, the Minister in charge of the Commonwealth Electoral Act, was concerned with the possibility of high numbers of exhausted votes, though in his second reading speech acknowledged that the formality requirement ``might have the effect of continuing to produce a fairly high informal vote''. Various coalition MHRs such as Dame Enid Lyons pointed out that marking all preferences was unnecessary, as experience in Tasmania had showed, and would surely lead to a high informal vote. Mr Archie Cameron, Member for Barker, moved an (unsuccessful) amendment to accept ballot-papers marked with at least as many preferences as there were vacancies, as in Tasmania. Eire, Malta and the ACT currently have the most liberal of formality provisions for quota preferential elections -- only a single preference is required. Exhausted votes have not been seen as a significant problem to date in these elections and informal voting is low: around 1% in the first two and around 4% in the ACT (the higher figure due in part to a remnant of the ``abolish self-government'' movement).