A month ago I wrote a guide to How Not to Report Opinion Polls. I have a history of starting regular features and then failing miserably to deliver them, but I am at least going to try to come back to it at the end of every month and highlight particularly poor reporting in the weeks just gone by.
For July I’m going to start with this report from the Independent, claiming that a ComRes poll shows “Dramatic change as two-thirds now support GM crop testing” and that “Public opinion appears to be shifting in favour of the development of genetically-modified crops, according to a ComRes survey for The Independent”.
ComRes found 64% of people agreed with a statement that “Experiments to develop genetically-modified crops should be encouraged by the Government so that farmers can reduce the amount of pesticides they use”. However, the article doesn’t mention any past results that it can be compared to in order to justify the claim that there has been a dramatic turnaround in support for GM crops.
Historical polling on the issue by MORI here does indeed suggest a much lower level of support for GM crops, but these differences could easily be explained by the question wording – MORI was asking things like “How strongly, if at all, would you say you support or oppose genetically modified food?” while ComRes’s statement specifically links the development of GM crops to a positive outcome of reducing the use of pesticides.
To see the impact asking different questions could make, look at this more extensive polling on the issue by Populus. Asked a generic question on whether or not GM food should be encouraged 27% of people say yes, 30% no. However, if you look down the survey to page 38 it asks specifically about whether people are supportive of using GM wheat to repel aphids and reduce the need for pesticides and finds 58% of people are supportive of this specific use. It seems plausible that the reason ComRes found such high support is not because of some great shift in support, but because their question specifically mentioned a popular potential outcome from GM.
If we want to see whether or not public support for GM actually is growing we need to have a question that has been asked consistently over time. This is surprisingly difficult to find – MORI don’t seem to have asked the question above again since 2004. The best I can track down is the Eurobarometer polling here, which every 3-5 years has asked if people agree that GM food should be encouraged. As you can see from the table on the first page, there is no obvious trend in the UK’s answers, support for encouraging GM food has moved by 45% to 25% to 35% over the years. Certainly the picture it shows is not one of a strong trend towards people supporting GM food.
(The Populus poll, incidentally, asked a similar question to the Eurobarometer question, but they can’t be directly compared either, not least because 43% of people told Populus they “neither agree nor disagree”, an option that the Eurobarometer did not offer. This, in turn, was misreported by the Daily Mail back in March.)
Once again, the lesson is to look at the polls in the round, not to take a single finding out of context, especially when it that question is one that is likely to put an issue in a particularly good or bad light. If you are looking at trends over time, you should always compare apples with apples. If two significantly different questions give different results it is as likely to be down to different wording as it is to a change in opinion, especially in cases like this.