The results of a new survey by the Pew Research Centre help provide an answer, with Sweden among the nations quizzed on the importance of issues like cultural norms, country of birth and language to national identity.
The good news for Sweden's foreign-born population is that one of the the things it's impossible to change is of little importance, with few Swedes making a strong connection between the place someone was born and their national identity.
Less than one in ten (eight percent) of Swedes polled responded that "having been born in our country is very important for being truly Swedish", the lowest of the 14 countries which were asked the question.
That is also less than the European median of 33 percent, and way below the 52 percent of Hungarians and 50 percent of Greeks who answered that birthplace is very important to be truly considered one of them.
Customs and traditions are also given little importance by the Swedes when it comes to assigning national identity, according to the survey. Only 26 percent of Swedes polled said that was the case, which again was the lowest of the 14 nations asked that question. Hungary had the highest level of agreement (68 percent) followed by Greece (66 percent).
There was however a notable difference in opinion on that issue depending on political sympathies. The survey showed a 24 percentage point difference on the importance given to Swedish customs and traditions by sympathizers of the populist Sweden Democrats (SD) compared to those who see the party unfavourably.
Of those who view SD favourably, 44 percent said sharing national customs and traditions is very important for being truly Swedish, while 20 percent of those who have an unfavourable view of SD said that was the case.
Similar divides were found when responses from sympathizers of Ukip in the UK and the National Front in France were compared with those who see the parties unfavourably.
The survey suggests that Sweden's reputation as a largely secular country is deserved. Only seven percent of Swedes think being a Christian is essential to their national identity, the lowest of the 13 nations asked that particular question. The majority (57 percent) said religion is not at all important to being a Swede.
Age also played much less of a role in Sweden in shaping that view than in many other countries. The 'oldest-youngest' gap in the country (the difference in opinion between those aged 18-34 and those aged 50 plus) on that subject was one of the lowest of the nations surveyed, with only eight percent more of Swedes aged 50 plus answering that Christianity is very important to national identity compared to those aged 18-34. In Greece there was a 26 percent difference.
So what exactly do Swedes think is important to be considered truly Swedish? Don't be fooled by the Swedish love of speaking English: according to the survey, the majority still think that being able to speak Swedish is key, with 66 percent saying speaking the national language is very important for being truly Swedish. Only two percent said it was not at all important.
The importance given to language was not unique to Sweden however. The majority in each of the 14 countries polled on the question said the same, and the median across Europe was 77 percent.
There does appear to be a generational shift taking place on the issue in Sweden though, with the youngest generation 23 percentage points less likely than the oldest generation to say language is very important to being Swedish. In the Netherlands the difference was 11 percentage points.
The moral of the story? Learn the local language if you ever want to be considered truly Swedish. At least for the foreseeable future, anyway.