Since the social classes in the United States do not have any clear boundaries, how is a sociologist supposed to determine whether their subjects are in the upper class or the upper-middle class?

According to several researches such as Dennis L. Gilbert and Leonard Beghley, there are several differences between middle class people, and upper middle class people.

Income and educational attainment are two of those differences, with upper middle class people being almost exclusively college-educated, a high percentage holding graduate degrees, while middle class people tend to have some high school educated people included.

Thus, the sociologist could survey the subjects of his study to find out about their education, their income, and also their social status.

A sociologist could draw from the theories of French sociologist Pierre Bourdeiu to draw boundaries for this last variable. Pierre Bourdieu explains that the difference in class does not depend only on variables such as income and education, but also in tastes, cultural and recreational activites, and even accent and language used. This variables could be summarized as social status, and a good sociologist would certainly use them in his or her studies.