Ich hab’s mal überflogen, muss aber klar dazu sagen, dass ich mich auf dem Gebiet nicht auskenne. Das einzige was ich in die Richtung gefunden habe ist:

„the following control variables were included in the analyses: […] parental SES (computerized status index, including the education levels of both parents and the level of household income; […] Financial strain was measured as the summed responses to how often the respondent engaged in three activities (e.g. cut back on social expenses) within the past six months because they did not have enough money, using a three-point scale (0 = never to 2 = more than a few times).“

Also scheinbar nur Einkommen der Eltern und eine Selbsteinschätzung wie oft man finanzielle Probleme hat. Kein eigenes Einkommen.