THE rise of populism in Europe and the United States has revealed that voters are deeply divided over immigration. Nationalists and populists, from Donald Trump to Britain’s UK Independence Party and Alternative for Germany (AfD), proclaim that governments should give priority to keeping foreigners out. But pinning down what exactly makes someone truly a national or a stranger is tricky. This is partly because identity is based on a nebulous mix of values, language, history, culture and citizenship.

A new poll by the Pew Research Centre, a think-tank, attempts to unravel the idea of how someone can be judged to be genuinely American, British or German. It asked respondents various characteristics—language spoken, customs observed, religion and country of birth—and how important they were to being a national of their country.

Where you live makes a big difference. On average over the 15 countries surveyed, speaking a state’s national tongue is seen as the most important trait. The Dutch rate this higher than anyone, whereas Canadians are the least concerned about linguistic ability, with only half saying that being able to converse in English or French (one of the two national languages) is very important. One reason may be that Canada is divided by language; another is that, along with Australia, it has the largest share of people born abroad among the countries polled, at over 20% of the population.

Recent experiences with immigration appear to affect different countries in different ways. People in Greece and Hungary, which have been transit countries for a large flux of migrants from the Middle East, place strikingly high importance on sharing customs and traditions, and being born in the country (Greeks also care strongly about being Christian). Yet in Germany, the ultimate destination for many of the refugees and migrants, respondents give comparatively little weight to such factors. That suggests that there may still be life in Willkommenskultur, or at least that the AfD party still has some way to go before becoming a real contender for power.