Janos Ladanyi and Ivan Szelenyi tried to analyse who is to be considered a member
of the Roma ethnic group in Bulgaria, Romania, and Hungary. Their data show that the
ethnic classification systems of the different countries exhibit crucial differences.
The system in Bulgaria appears to be stable and its ethnic boundaries much more rigid
than in the two other countries. One could also argue that the Bulgarian system of
ethnic boundaries to a certain extent resembles the US system of ethnic boundaries,
whereas the Hungarian and Romanian model seems to have much more in common with the
Brasilian system. The presented research data support the theory that anthropological,
biological, and genetic criteria are rather of secondary importance for ethnic classifications,
which seems to be rather more determined by basic social mechanisms.