An example of a stratum class model was developed by the sociologist William Lloyd Warner in his 1949 book, Social Class in America. For many decades, the Warnerian theory was dominant in U.S. sociological theory.

Based on social anthropology, Warner divided American into three classes (upper, middle, and lower), then further subdivided each of these into an "upper" and "lower" segment, with the following postulates:

1. Upper-upper class. "Old money." People who have been born into and raised with wealth.
2. Lower-upper class. "New money." Individuals who have become rich within their own lifetimes.
3. Upper-middle class. High-salaried professionals (i.e., doctors, lawyers, corporate executives).
4. Lower-middle class. Lower-paid professionals, but not manual laborers (i.e., police officers, non-management office workers, small business owners).
5. Upper-lower class. Blue-collar workers and manual laborers. Also known as the "working class."
6. Lower-lower class. The homeless and permanently unemployed, as well as the "working poor."

To Warner, American social class was based more on attitudes than on the actual amount of money an individual made. For example, the richest people in America would belong to the "lower-upper class" since many of them created their own fortunes; one can only be born into the highest class. Nonetheless, members of the upper-upper class tend to be more respected, as a simple survey of U.S. presidents may demonstrate (i.e., the Roosevelts; John Kennedy; the Bushs)

Another observation: members of the upper-lower class might make more money than members of the lower-middle class (i.e., a well-salaried factory worker vs. a secretarial worker), but the class difference is based on the type of work they perform.

In his research, findings, Warner observed that American social class was largely based on these shared attitudes. For example, he noted that the lower-middle class tended to be the most conservative group of all, since very little separated them from the working class. The upper-middle class, while a relatively small section of the population, usually "set the standard" for proper American behavior, as reflected in the mass media.