The referendum to repeal the Eighth Amendment to the Constitution is the 40th referendum held since the State was founded.
The highest turnout in any referendum was for adoption of the 1937 constitution, which saw 75.8 per cent of voters cast their ballots.
The next-highest turnout was for the referendum on accession to the then European Economic Community in 1972, at 70.9 per cent.
The lowest-ever turnouts in referendums were for two held together in July 1979. One was to ensure that orders made by the Adoption Board could not be declared unconstitutional because they were not made by a court, and the other was expanding the university seats in the Seanad beyond representation for the National University of Ireland and Trinity College.
The last two referendums – held on the same day in 2015 on same-sex marriage and reducing the age of eligibility for presidential candidates – recorded a turnout of 60.5 per cent.
The poll to introduce the Eighth Amendment in 1983 recorded a 53.7 per cent turnout. The turnout in the 1992 referendums on abortion – on the right to life of the unborn, the right to travel and the right to information – was just over 68 per cent. In the 2002 abortion referendum, turnout was 42.8 per cent.