The government has announced that EU citizens will not be eligible to vote in the referendum on Britain’s membership of the EU. However, because the electoral roll will be the same as that used in the general election, citizens of certain Commonwealth countries will be able to vote.
The question about who ought to be able to vote in a referendum like this is a normative one. From what I can tell, normative theorists, often building on the "all affected interests" principle, tend to support broader franchises, and would typically support extending the franchise to EU citizens. Certainly, I’m not aware of any principled argument why Maltese citizens should be able to vote but Greeks shouldn’t.
There is, however, a separate empirical question: would extension of the franchise make any difference to the outcome?
According to wave 4 of the British Election Study (fieldwork: March 2015), 50.2 percent of British citizens supported Britain staying in the EU.
In that same survey, 81.5 percent of EU citizens resident in the UK supported Britain staying in the EU.
According to the latest ONS Population by Country of Birth and Nationality Report, there are 57678 thousand resident Britons, and 2507 thousand resident EU citizens, or roughly 23 British citizens for every EU citizen.
If we assume that the two groups vote at similar rates,1 the difference between a Britons-only referendum and a Britons-plus-EU-citizens referendum is the difference between:
- (57678)/(57678+2507) * 50.2 + (2507)/(57678+2507) * 81.5, or 51.5%
Therefore the votes of EU citizens, although they will make Brexit less likely, will only matter in a very close referendum. The choice of electoral roll is thus in a very real sense a matter of principle rather than political practice.
This assumption is likely false. On the one hand, a slightly greater proportion of EU citizens resident will be eligible to vote in virtue of being over 18. On the other hand, turnout amongst the eligible is likely to be lower amongst EU citizens. EU citizens were eligible to vote in the Scottish independence referendum — but whilst 90.5% of British respondents said that it was "very likely" that they would vote, only 63% of EU respondents said the same.↩