A referendum on lowering the voting age from 21 to 20 was held in Denmark on 21 September 1971.Dieter Nohlen & Philip Stöver (2010) Elections in Europe: A data handbook, p524 The change was approved by 56.5% of voters, with a turnout of 86.2%.Nohlen & Stöver, p533 A previous referendum had been unsuccessful in lowering the electoral age to 18 years, which was introduced after a 1978 referendum and which still stands.
Results ChoiceVotes%For1,601,75656.5Against1,231,79243.5Invalid/blank votes78,201–Total2,911,749100Registered voters/turnout3,378,08786.2Source: Nohlen & Stöver
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