It seems important to mention that the study looks at the behaviour of a few hundred people in Italy and Sweden playing a _game_ which simulates earning money,

It seems important to mention that the study looks at the behaviour of a few hundred people in Italy and Sweden playing a _game_ which simulates earning money, paying tax and possibly being audited. I.e. the study is not actually about the compliance rate of real taxation. tptacek's description of the paper he cites, i.e. "Here's a study comparing Sweden's compliance rate with that of Italy's, and finding them roughly similar" leaves out the crucial point that the whole paper is about a game, not real taxes.