How many people support gay marriage?

Various groups are touting polls that they claim show at one extreme 70% of people opposed to gay marriage, and at the other 65% in support. What's the real picture?

The cause of the disparity is party my old bug bear of questions asked as an agree/disagree statement grid. I have railed about these in the past, but in short, while such questions have their specific uses, they are extremely vulnerable to bias.

Let's start with basic principles. If you are seeking to find out what people's opinion is on same-sex marriage, a good place to start is a question along the lines of "Do you support or oppose legalising same-sex marriage?". A possible drawback with this is the issue of civil partnerships, which colloquially many people may think of as gay marriage. Given the issue currently at hand is whether to allow couples of the same sex to marry or just enter a civil partnership, we should really make that clear in the question.

This is basically the approach ICM took in their Sunday Telegraph poll:

"You might be aware that currently the law allows gay people to enter civil partnerships but they cannot get married. The Prime Minister, David Cameron wishes to legalise gay marriage but some senior members of both the Catholic Church and the Church of England are opposed. Do you support or oppose the move to legalise gay marriage?"

They found 45% supported legalising gay marriage and 36% opposed gay marriage, with 19% of people saying don't know. YouGov took a similar approach, but offered people a three way choice - supporting gay marriage, supporting civil partnerships but not gay marriage or opposing both gay marriage and civil partnerships.

Since 2005 same-sex couples have been able to enter into civil partnerships. While civil partnerships offer the same legal rights as marriage, same-sex couples are not able to marry. Which of the following best reflects your view? I would support same-sex marriage

I support civil partnerships, but would oppose samesex marriage I oppose both civil partnerships and same-sex marriage Don't know

They found 43% support for same-sex marriage, 32% support for civil partnership but not gay marriage, 15% opposed to both and 10% sayibng don't know. Clearly the proportion of people supporting gay marriage is almost identical, but the more nuanced options for those opposed to gay marriage has led to some people who would otherwise have said don't know giving an opinion.

The other two polls at the extremes were both agree/disagree statement grids. The poll that showed the most support for same-sex marriage, from Populus, asked:

Do you agree or disagree with the following statements? Gay couples should have an equal right to get married, not just to have civil partnerships

They found 65% of people agreed, and 27% disagreed with 8% saying don't know. They also asked whether people agreed with the statement that "Gay couples should have exactly the same rights as heterosexual couples" which was agreed with by 76% of people. The tables make it unclear whether the order of the statements was rotated, or whether they were asked in the order presented with the marriage question first.

The Populus question itself is fairly straight forward, the higher level of support is probably due to the the agree/disagree statement structure - it is asking if people agree or disagree with a statement in favour of gay marriage, casting it as an issue of equal rights.

Compare and contrast it with this poll conducted by ComRes for the Coalition for Marriage, which asked if people agreed or disagreed with the statement:

"Since gay and lesbian couples already have the same rights as married couples available to them under civil partnership, they should not be allowed to redefine marriage for everyone else"

This is essentially asking if people agree with a statement opposed to gay marriage, casting the it an issue of a minority imposing their views on the majority. Asked that way, 51% agreed with the statement and 34% disagreed (so inferring that only 34% supported gay marriage).

Finally the 70% figure being quoted by opponents of gay marriage comes from this poll by ComRes for Catholic Voices, which asked if people agreed with the statement that:

"Marriage should continue to be defined as a life-long exclusive commitment between a man and a woman"

70% of people agreed, with 22% disagreeing. Here we have a statement that doesn't even mention same-sex marriage, being rather overinterpreted by people for their own ends. Perhaps the logical inference is that anyone agreeing to this statement must be opposed to the laws on marriage being changed so that same sex-couples can marry (though, by the same rather tendentious logic, one could infer that 70% of people must think that divorce should also be made illegal), but in this case, we have other questions in other polls that actually asked directly about gay marriage, so we can be fairly certain that 70% of people are not interpreting the sentence that way.

I would again urge people to be cautious about polling questions asking if people agree/disagree with a loaded statement. It is rarely the best way of asking a question and carries with it risks of bias. If there are a conflicting polls on a subject, do not cherry pick those that suit your own views - take a broad look across all the polls. In this context, when the argument is cast in terms of equal rights a majority support gay marriage, when cast as a minority imposing their views upon the rest a majority are opposed - when asked simply and directly just under half are in support.

UPDATE: Sean Fear in the comments section has pointed out an Angus Reid question on gay marriage. They asked a similar question to YouGov, but without some of YouGov's explanatory text:

Now, thinking about same-sex couples. Which of these statements comes closer to your own point of view on the legal recognition of same-sex couples in the UK? Same-sex couples should be allowed to legally marry Same-sex couples should be allowed to form civil partnerships Same-sex couples should not have any kind of legal recognition Not sure

Their results were again pretty similar to YouGov and ICM - they found 43% in favour of gay marriage, 34% in favour of civil partnerships but not marriage, 15% opposed to both.