The marketing and consumer behavior literature has traditionally suggested that customer satisfaction is a relative concept, and is always judged in relation to a standard (Olander, 1977). Consequently, in the course of its development, a number of different competing theories based on various standards have been postulated for explaining customer satisfaction. 

A generation is a group of people born around the same time and raised around the same place. People in this “birth cohort” exhibit similar characteristics, preferences, and values over their lifetimes.

Theories are explanations of a natural or social behaviour, event, or phenomenon. More formally, a scientific theory is a system of constructs (concepts) and propositions (relationships between those constructs) that collectively presents a logical, systematic, and coherent explanation of a phenomenon of interest within some assumptions and boundary conditions (Bacharach 1989).

Research is a systematic investigation or inquiry aimed at discovering, interpreting, and revising facts, theories, events, behaviors, or phenomena.