The graph shows the results of the national referendums on liquor licensing, held from 1911 until 1987. The Licensing Amendment Act 1910 allowed electors to vote for national continuance or national prohibition. In December 1919 a third option, state purchase and control of liquor, was added. The prohibition referendum was usually held at the same time as the general election. The exception was April 1919, when a special referendum was held on the prohibition question. Initially 60% of the vote was required for prohibition to become law. From April 1919 only a bare majority was needed.