US Insights

2017: A good year for the pollsters

Jon Puleston

VP of Innovation

Politics 12.21.2017 / 00:02

vote-polling-french-election

Global election polls have been at their most accurate this year, Lightspeed data shows

Research by Kantar reveals that ‘the polls’ consistently predicted the correct outcome of every major national election held in 2017.

A study by Kantar’s Lightspeed has pointed to 2017 as a highly successful year for the polling industry. Of the 15 major international legislative and presidential election votes in 2017 where polling was conducted and published, the winning outcome was correctly forecast in all 15, and 14 out of 15 did so with an accuracy better than the international norm.

Overall, the average polling error for the 15 elections was just +/-1.9%, 24% lower than the international norm of +/-2.5%. (The international norm is based on Kantar’s international polling database of 31,000 polls covering 470 historical elections from 1936 to 2017.) The chart below illustrates the results across the 15 major elections.



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Polling companies around the world are judged by how accurately their polling projections predict the outcome of elections, so an exceptionally consistent year like this is worthy of some recognition.

In the UK this year, the polling industry predicted the result of the General Election with an average absolute error of +/- 1.5%, significantly lower than the +/- 1.9% international average for 2017. This is perhaps because of improvements made after the UK polling council review of methodology.

Other insights from the year-end analysis include:

Most accurate country:

The most accurate polls of 2017 came from France during the first round of the Presidential Election. It was a close vote with just a 5% margin separating the fourth candidate on 19% from the first on 24%. Compared to the industry average polling error for first round votes of +/-6%, the 2017 polls predicted the result with an accuracy of +/-0.2% resulting in the most accurate polling results in French history.

Most consistent country:

For the fourth election in the row, the German polling industry forecasted the result in under +/- 1.5% accuracy. The average absolute error for this year’s election was +/- 1.2%.

UK polling results outperform international average:

In the UK this year, the polling industry predicted the result of the General Election with an average absolute error of +/- 1.5%, significantly lower than the +/- 1.9% international average for 2017. This is perhaps because of improvements made after the UK polling council review of methodology.

2015/6 election learnings:

Three prominent polling misreads in a row (the 2015 UK general election, Brexit vote and US Presidential election) led many people to question the validity of polling. A detailed post mortem evaluation of these miscalled results in the wider context of international polling norm illustrates four key points:

  • The importance of weighting transparency – so that the models behind forecasts are understood
  • Better sampling – especially in accounting for the growing importance of the over 75s as a voting block
  • More confidence in polling models – less tinkering by individual polls to better fit with the herd
  • The value of learning and sharing best practice techniques used by pollsters around the world - for example how to account for ‘shy voter effects’ and more effectively measure voter turnout.

"Polling is an enormously valuable insight into the pulse of public opinion," said Dr Michelle Harrison, CEO at Kantar Public. "We shine a light on the issues and concerns that make up the story of every unique election and support transparent democracy. At Kantar, we are investing and innovating to continue delivering accurate and insightful polling; overcoming the ever-evolving political, economic, social and geographic shifts." 

For more information, read the full report here.

Source: Lightspeed, Kantar Public

Editor's Notes

*Average errors are based on the poll on poll average absolute errors for the top 4 parties from all opinion polls conducted 7 days before the election unless stated.

To speak with the author or for inquiries, contact us. Follow @Kantar and sign up for our insight alerts.

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