Which variable is the best predictor of one's own class position as an adult?

What class one belongs to is determined by the relations of production at work. If one merely sells one's physical labour ie is a wage slave then one is from the working class. If one sells one's ideas or owns a small business then one is from the petit bourgeosie. If one owns the means of production, then one will belong to the bourgeosie.

Possible predictor of one’s class position as an adult could be their socioeconomic status. Socioeconomic status refers to a person’s position with regards to income, education and occupation determined by academic and work experience, and their social relations. Today, the factor of socioeconomic status highly reflects a person’s sense of achievement and fulfillment in life although discounting the significance of psychological and other factors such as awareness and self-actualization to determine a person’s status.