Unethical People Lie about Their Social Background

According to a recent paper in PNAS (summarized here), upper-class people are more likely to be unethical. The trouble is, people were sometimes judged as upper class on the basis of their claims. It looks like they just proved that unethical people lie about their social background. By the way, what was the claimed social class of the investigators? If they were upper class then this study reminds me of the classic song How Could You Believe Me When I Said I Loved You When You Know I've Been a Liar All My Life?

In part of the study, class membership was judged by the objective standard of what cars were driven by the subjects. This ran into the trouble that it was based on a small sample.