Predicting turnout for the EU referendum is harder than previous elections, a Welsh political expert has said.
Professor Roger Scully from the Wales Governance Centre said it could be anything between 55% and 70%.
"This is such a hard poll to call on turnout. Looking at polling evidence and interest in the TV debates, I suspect it could be mid to low 60s".
Her added: "I think that a low turn out could benefit those who want the UK to leave the EU. The leave supporters are passionate and will vote. A higher turnout could benefit the remain camp as you could get more younger voters and people who are OK with the status quo coming out".
More than two and a quarter million people in Wales have registered to vote in the EU referendum.
Across the UK, including Gibraltar, more that 46.5m people have registered.
That's a record according to the Electoral Commission with 150,000 more people able to vote than in last year's general election.
In the 1975 referendum on European Community membership, Wales had a turnout of 66.7%, which was higher than that in England, Scotland and Northern Ireland.
May's Assembly elections saw a 44% turn out and last year's general election saw 65.6% in Wales.