They describe theirs better, but yes, I believe so. Here’s European value study’s methodology.
www.europeanvaluesstudy.eu/page/methodology
They ask people questions and then make statistics from that. But it’s beside the point imo. When it comes to how they formulate the questions, all it says is:
"The questionnaire administered by survey interviewers was designed by Pew Research Center staff in consultation with subject matter experts and advisers to the project."
I have a feeling it's not about methodology, but rather how you define "christian" (I guess that’s strictly speaking part of the methodology too, though). Notice that in Eauopeanvaluestudy they are asking the same thing, but with a different angle, which gives a different result.
Since 1990 the number of members of the Lutheran state-church of Denmark has declined steadily from 90% to 76%. Number of baptisms are down from 80% in 1990 to 62% in 2017 (obviously muslim immigration also is a factor here, but not the sole one) Hows that for christianity growing in Denmark? Yes, culturally some people are maybe reclaiming a cultural christian identity as a defence against muslim immigration, but it's just superficial.
Add to that, that you have to understand that just because people are members of the state-church because they were baptized by their parents, it doesn’t mean they believe in Jesus Christ or even god. It’s just a tradition. You can read about the danes relationship to their state-church here, if interested:
https://international.kk.dk/artikel/are-danes-religious
We actually even had a priest of the state-church in 2003, who openly declared he didn’t believe in god. It did cause some debate of cause.
https://en.wikipedia.org/wiki/Thorkild_Grosbøll
Also......
“According to a 2009 poll, 25% of Danes believe Jesus is the Son of God, and 18% believe he is the saviour of the world.”
Source:
https://en.wikipedia.org/wiki/Church_of_Denmark#Faith_and_church_attendance (the original source of the quote is from a yougov study. I’ll see if I can dig it up somewere in english if I have time)
If you don’t believe Jesus Christ is the savior of the world, then you’re not a real Christian - because you don’t believe in the god of the new testament. Otherwise I'd label you: "a spiritual person from a christian culture". What could be called a “cultural Christian”. Many danes selfidentify as christians, while in reality - they're strictly speaking not.
But can you believe in a pantheistic and un-personal God, and still call yourself christian? Of cause you can - because religions are ideas, and like all other man-made ideas, they can be put into all kinds of constellations with other ideas that shouldn’t fit together. And you don’t have to be consequent. I mean, can you be a neonazi skinhead and a jew at the same time? Of cause you can. Humans are full of contradictions and absurdities like that.
The question,
“are you a christian?” doesn’t neccesarily mean the same in the ears of a Scandinavian “cultural Christian” protestant and a southern European catholic.
All that said, the more I think about it, maybe it’s just me misreading the infographics. But I do think that these kind of studies are hard to make, because you are trying to fit something very complex - what people think - into some small bars representing one simple sentence. Or maybe it’s just me splitting hairs and being to anal about semantics. Could be.