It’s hard to directly compare a country to a city, as it’s reasonable for someone to live outside the city and commute in for work, while someone can’t really live in Germany and commute into Denmark for work.
If we’re going to try to compare a country to a city, we need to look at where within the city they’re going to live. NYC prices vary hugely from neighborhood to neighborhood. I don’t know how things vary in Denmark. And there’s also policy issues such as rent control.
Regardless, given the local purchasing power index is 165 in Denmark, that would imply that the minimum wage should be lower relative to pricing by 40%, as Denmark is richer than NYC. If we want to take the line that we want to directly compare NYC to Denmark, the appropriate minimum wage would have to be 40% lower than Denmark’s, so that would be $9.10/hr.
Edit: Looked it up. Denmark’s minimum wage is 103 DKK which is $15.18 at current exchange rates. Not $20.