Weeks of debate on same-sex marriage may not have shifted Australians' votes on the issue, according to a poll that has found 60 per cent support for change.

The survey taken by YouGov on the eve of the plebiscite result found that hearing the key arguments for and against allowing same-sex marriage "appear to have very little impact on whether respondents support it" according to an analysis by the US Studies Centre at the University of Sydney, which commissioned the survey.

The centre's poll, which also canvassed views in the United States, found that Americans are more likely than Australians to support the right of business owners to refuse services for same-sex weddings because they have religious objections. But the difference was not huge, with 50 per cent of Americans and 43 per cent of Australians saying business owners should have the right to refuse.

Those disagreeing or not having a position were 35 per cent and 15 per cent in the US, and 39 per cent and 17 per cent in Australia.