The problem with opinion polls, in Hong Kong and elsewhere

The Conservative Party's wide, clear-cut margin of victory in the British general election surprised many people as the party claimed its first outright majority since 1992, despite what many opinion polls were predicting. The inaccurate result has led the British Polling Council to set up an inquiry to find out why the final polls were so wide of the mark after pollsters dramatically understated the Conservative share of the vote.

There have been suggestions that it was due to the "shy Tory" effect; voters were perhaps unwilling to admit publicly they supported the party and, indeed, online pollsters routinely found higher levels of support for the Conservatives than did telephone polls. Another possible explanation is that the Labour Party failed to turn those who pledged support into actual votes on the day.

Here in Hong Kong, the government is frantically trying to win over public support for its reform package, with a massive TV campaign, advertisements in the MTR, and officials on the ground appealing to the people. However, the latest joint university polling results seem to show support is waning - 42.3 per cent supported the package and 40.9 per cent opposed it. An earlier poll showed that 46.7 per cent supported reform and 36.7 per cent opposed it. It would seem that more people still support the package than are against it, but the gap seems to be narrowing since the government began its campaigning. But how much can we trust the results?

All such results are basically derived from phone polls. The polling organisation usually uses a standard, territory-wide phone sample. A computer randomly generates the numbers for pollsters to call. Within each household reached on a landline, an interview is sought with a person living in the household who is 18 or older. When respondents are selected in this way, at random, every adult has an equal chance of being part of the sample, which is typically about 1,000 adults. Sometimes, more detailed subgroup analysis is provided but with a smaller sample size, the accuracy of the results is reduced. Some weighting of respondents might be applied, for age and gender usually, to match the demographic characteristics of the adult population according to data from the Census and Statistics Department.

So, could the problems experienced in the UK also affect our polling results? Those contacted by phone may be less willing to admit they support the reform proposal. And among those who did express support for the proposal, would they actually cast a vote in a 2017 territory-wide election? One of our research studies on the post-80s generation, in 2011, showed that less than 40 per cent of those aged 18-30 had registered to vote and their turnout rate in the previous Legco election was less than 50 per cent. Even though a high proportion of young people oppose the government's reform proposal, according to phone polls, if a referendum were held today, I wouldn't be surprised to see different results to those in the poll.

Conducting a poll properly is as much an art as it is a science. The questions need to be simple and clear, with no ambiguity, and there should be no leading or loaded questions, in order to achieve an unbiased response. The timing of the survey is important, too. If a poll is conducted during the day, it can be difficult to get hold of members of the working population, who might have different views from those who are at home. The response rate is also very important, and anything less than 50 per cent should be viewed cautiously.

Sometimes, in order to achieve a larger sample size, the pollsters collect information over a short time frame from those willing to take part in the survey. But that doesn't mean the results will be better, especially if there are some groups of the population who still cannot be contacted. A representative sample is more important than a large one.

Even the famous polling company, Gallup, gets it wrong. Its polls have correctly predicted the winner of the US presidential election, with a few notable exceptions. In the 1948 contest between Thomas Dewey and Harry S. Truman, most pollsters wrongly predicted a Dewey victory. In 1976, they inaccurately projected a slim victory for Gerald Ford over Jimmy Carter. And, in 2012, Gallup's final election survey had Mitt Romney at 49 per cent and Barack Obama at 48; the final results showed Obama gaining victory with 51.1 per cent to Romney's 47.2.

Based on latest poll results for the 2017 chief executive election (if we can still believe them), efforts to promote or oppose the government proposal don't seem to have been effective in breaking the deadlock. Wouldn't it be better if both sides could spend more energy and effort to improve the proposal and reach a compromise? If politics is the art of compromise, neither side has scored well.

Polls aren't helping to solve the problem. The pan-democratic camp and government are still appealing to the community for more support, in order to trumpet this in the polls. So far, unfortunately, the issue has just caused further damage by polarising the community. It is time to look at where we are heading.

We don't seem to understand the real meaning of consensus. The word derives from the Latin con, meaning "together with," and sentir, meaning to think or feel, hence, "to think or feel together". A consensus doesn't imply total agreement; it is not about trying to get everyone to agree. Instead, it is about finding the best ideas for a society. It's important to make sure everyone's voice is heard and debates are framed around this premise. Then we can move on.

Paul Yip is a professor of social work and social administration at the University of Hong Kong