Aside from the overall veracity of "Swedish think tanks", it would really help to have a link;
I would suspect the above to be somewhat related to property prices. If you don't own your home, you are f*cked in the big cities (oh yeah, you can also spend half your life in a queue for a rental place).
Still, I would rather be "poor" in Sweden than the US as I would never worry about healthcare expenses, worry less about education for my hypothetical children (Swedish school system though very well funded sucks for different reasons), etc.
(Yeah I am from and living in Sweden.)