The 15th of July marks the birthday of feminist activist Emmeline Pankhurst, born 159 years ago in Manchester, who spearheaded the suffragette movement.
Her ultimately successful fight for women’s voting rights remains one of the most important milestones in changes to the laws governing the electorate in the UK over the last 185 years.
Yet the size and shape of the UK electorate has not changed markedly since 1969 when the voting age was reduced from 21 to 18.
Proportion of population registered to vote in UK general election1, 1885 to 2015
But what impact would lowering the voting age from 18 have in UK elections?
Lowering the voting age to 16 is something that has already been introduced in Scotland for elections to the Scottish Parliament, and at a UK level the different political parties have mixed positions.
In the lead up to the 2017 general election several political parties, including Labour, Liberal Democrats, SNP, Green Party and Plaid Cymru, pledged to give the vote to 16- and 17-year-olds. But what do ONS population estimates tell us about how this might change the voting population?
In 2015, the most recent year for which we have constituency-level population estimates, there were 1.5 million 16- and 17-year-olds in the UK. They would have made up 2.87% of the population aged 16 and over.
Which areas might have been affected during the 2017 general election?
Overall there were 88 constituencies2 where the number of 16- and 17-year-olds3 was greater than the winning margin. This doesn’t mean that the outcome in the seats would have changed, that would depend on voter turnout and preference, but it does show us those areas where there would have been potential for change.
Four of the 10 constituencies with the smallest margins were in Scotland, with the constituencies of North East Fife, Perth and North Perthshire, Glasgow South West and Glasgow East all with a majority of 75 or less.
Constituencies where the 16- and 17-year-old population was greater than the winning margin, UK, 2017
In fact there were 19 constituencies in Scotland where the 16- and 17-year-old population is higher than the margin in 59 constituencies (32%). This compares with 22% of constituencies in Northern Ireland, 17.5% in Wales, and 10.5% in England.
Proportion of seats with 16- and 17-year-old population greater than winning margin, UK, 2017
Which areas would have the greatest share of 16- and 17-year-old voters?
Of course the areas with the tightest margins will change from election to -election, so another way to look at this is to explore the areas with the largest proportion of 16- and 17-year-olds. The proportion of 16- and 17-year-olds in the population age 16 and over might give us a sense of this population's potential to influence the election outcome.
However, care must be taken in using these data to assess the potential impact on election outcomes as these population estimates include some people who are not eligible to vote (for example foreign nationals) and exclude some people who are eligible to vote (for example overseas electors).
Birmingham and Bradford had the largest proportion of 16- and 17-year-olds, as a share of those aged 16 and over. The Birmingham Hodge Hill constituency stood at almost 5% (4.85%), followed by Bradford West (4.38%), Bradford East (4.21%) and Birmingham, Hall Green.
Proportion of 16- and 17-year-olds in population aged 16 and over, UK, 2015
The smallest proportions of 16- and 17-year-olds were found in Battersea (1.48%), Glasgow North (1.54%) and Glasgow Central (1.58%).
Timeline of UK electoral change
The Great Reform Act of 1832 introduced voter registration, broadened those who could vote (although the working class largely remained ineligible to vote), and created new seats in England and Wales.
Prior to the Great Reform Act, voting was limited by the fact that two-thirds of MPs stood for election in uncontested seats, meaning for much of the country, voting was not even possible.
In 1867 another Great Reform Act extended the vote to all householders, which gave the vote to many working class men who had previously been excluded from voting. It was not until the 20th century that significant changes were made to electoral law that dramatically changed the number of people who were eligible to vote.
By 1908, the vote was limited to men over 21 who “paid rates” or owned property. This is estimated at about 60% of the adult male population.
The Representation of the People Act 1918 extended the vote so there was no longer a property qualification for men. More famously, perhaps, it extended the vote to women at parliamentary elections, though this was limited to those over 30, and the property qualification still applied to them.
The 1918 Act added 13.7m women and 5.3m men to the electorate. Had women been given the vote on equal terms with men, as they eventually were in 1928, they would have been in the majority, due to loss of men during the war.
Full electoral equality was not achieved until 1928, and the franchise as we know it today did not emerge until 1969, when the voting age was reduced from 21 to 18.
In 2015 a bill allowing 16- and 17-year-olds to vote in the Scottish and local government elections has been passed unanimously at Holyrood.
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Exact figures for the number of people eligible to vote are limited in accuracy, because not every UK resident is eligible to vote, and not every British citizen eligible to vote resides in the UK.
For the purposes of this analysis we are using Westminster Parliamentary constituencies as used in the UK general elections.
For the purposes of this analysis we have rolled forward the number of 14- and 15-year olds from the 2015 mid-year population estimate constituency figures to act as a fairer comparison with 2017 general election data