Online opinion polls 'may be overestimating support for Brexit'

Online opinion polls in the run-up to May 5 elections across Britain overstated support for the UK Independence Party, suggesting they may also be overestimating backing for leaving the EU, according to a leading polling analyst.

For months, pollsters have been aware of the difference in outcome between online and telephone polling on the question of EU membership.

With the referendum on a so-called Brexit coming on June 23, online polls put the two sides neck-and-neck, while telephone polls have the ‘Remain’ side in the lead. 

Last week’s elections offered an opportunity to check their findings.

According to Matt Singh of Number Cruncher Politics, 10 of the 12 online polls conducted in the two weeks before the vote overstated UKIP support. 

In polling for the London and Welsh assemblies, the online polls were on average three to four percentage points too high.

“Support for leaving the EU and votes for a pro-Brexit party are clearly not the same thing,” Mr Singh wrote on his blog.

Still, “online panels seem to be too Leave-y”, he wrote.

Following last year’s collective failure by pollsters to correctly predict the UK general election result, the reliability of opinion research companies has been under scrutiny. 

An investigation concluded there was no easy solution to the problem.

Mr Singh, who argued just before last year’s vote that the polls were understating Tory support, has suggested that part of the problem for Brexit polling may be that online polls have too many social conservatives in their samples.

Yesterday, sterling which has reacted with Brexit opinion polls was underpinned by increasing international support for the British campaign to remain in the EU. 

The UK’s total trade deficit narrowed to £3.8bn (€4.8bn) in March from a revised £4.3bn in February.

“The market appeared to be cutting down on sterling short positions, and deficit data that’s not as bad as expected by the market helped as a catalyst,” said Neil Jones, head of hedge-fund sales at Mizuho Bank in London.

Five former Nato secretaries general and 13 former US foreign, defence, and security chiefs said a UK withdrawal from the EU would weaken both the UK and the bloc. 

Sterling strengthened 0.2% to 78.84p against the euro.

Paddy Power said yesterday the probability of the UK leaving the EU was 30%, while the Remain vote stood at 75%.

Bloomberg and Irish Examiner staff

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