quality:correction
Generational theory

The sociologist Karl Mannheim was a seminal figure in the study of generations. He elaborated a theory of generations in his 1923 essay The Problem of Generations. He suggested that there had been a division into two primary schools of study of generations until that time. Firstly, positivists such as Comte measured social change in designated life spans. Mannheim argued that this reduced history to "a chronological table". The other school, the "romantic-historical" was represented by Dilthey and Martin Heidegger. This school focused on the individual qualitative experience at the expense of social context. Mannheim emphasised that the rapidity of social change in youth was crucial to the formation of generations, and that not every generation would come to see itself as distinct. In periods of rapid social change a generation would be much more likely to develop a cohesive character. He also believed that a number of distinct sub-generations could exist. According to Gilleard and Higgs, Mannheim identified three commonalities that a generation shares:

Mannheim elaborated on the meaning of a generation's "location" (Lagerung), understood in a historical, economic and sociocultural sense. In 1928 he wrote:

The fact that people are born at the same time, or that their youth, adulthood, and old age coincide, does not in itself involve similarity of location; what does create a similar location is that they are in a position to experience the same events and data, etc., and especially that these experiences impinge upon a similarly 'stratified' consciousness. It is not difficult to see why mere chronological contemporaneity cannot of itself produce a common generation location. No one, for example, would assert that there was community of location between the young people of China and Germany about 1800. Only where contemporaries definitely are in a position to participate as an integrated group in certain common experiences can we rightly speak of community of location of a generation.

One of the implications is that the chronological boundaries often attributed to different generations ("Generation X", "Millennials" etc.) have little global validity since these boundaries are mostly based on shared Western, especially American, historical and sociocultural 'locations'.

Authors William Strauss and Neil Howe developed the Strauss–Howe generational theory outlining what they saw as a pattern of generations repeating throughout American history. This theory became quite influential with the public and reignited an interest in the sociology of generations. This led to the creation of an industry of consulting, publishing, and marketing in the field (corporations spent approximately 70 million dollars on generational consulting in the U.S. in 2015). The theory has alternatively been criticized by social scientists and journalists who argue it is non- falsifiable, deterministic, and unsupported by rigorous evidence.

There are psychological and sociological dimensions in the sense of belonging and identity which may define a generation. The concept of a generation can be used to locate particular birth cohorts in specific historical and cultural circumstances, such as the " Baby boomers ". Historian Hans Jaeger shows that, during the concept's long history, two schools of thought coalesced regarding how generations form: the "pulse-rate hypothesis" and the "imprint hypothesis." According to the pulse-rate hypothesis, a society's entire population can be divided into a series of non-overlapping cohorts, each of which develops a unique "peer personality" because of the time period in which each cohort came of age. The movement of these cohorts from one life-stage to the next creates a repeating cycle that shapes the history of that society. A prominent example of pulse-rate generational theory is Strauss and Howe's theory. Social scientists tend to reject the pulse-rate hypothesis because, as Jaeger explains, "the concrete results of the theory of the universal pulse rate of history are, of course, very modest. With a few exceptions, the same goes for the partial pulse-rate theories. Since they generally gather data without any knowledge of statistical principles, the authors are often least likely to notice to what extent the jungle of names and numbers which they present lacks any convincing organization according to generations."

Social scientists follow the "imprint hypothesis" of generations (i.e., that major historical events—such as the Vietnam War, the September 11 attacks, the COVID-19 pandemic, etc.—leave an "imprint" on the generation experiencing them at a young age), which can be traced to Karl Mannheim's theory. According to the imprint hypothesis, generations are only produced by specific historical events that cause young people to perceive the world differently than their elders. Thus, not everyone may be part of a generation; only those who share a unique social and biographical experience of an important historical moment will become part of a "generation as an actuality." When following the imprint hypothesis, social scientists face a number of challenges. They cannot accept the labels and chronological boundaries of generations that come from the pulse-rate hypothesis (like Generation X or Millennial); instead, the chronological boundaries of generations must be determined inductively and who is part of the generation must be determined through historical, quantitative, and qualitative analysis.

While all generations have similarities, there are differences among them as well. A 2007 Pew Research Center report called "Millennials: Confident. Connected. Open to Change" noted the challenge of studying generations:

Generational analysis has a long and distinguished place in social science, and we cast our lot with those scholars who believe it is not only possible, but often highly illuminating, to search for the unique and distinctive characteristics of any given age group of Americans. But we also know this is not an exact science. We are mindful that there are as many differences in attitudes, values, behaviors, and lifestyles within a generation as there are between generations. But we believe this reality does not diminish the value of generational analysis; it merely adds to its richness and complexity.

Another element of generational theory is recognizing how youth experience their generation, and how that changes based on where they reside in the world. "Analyzing young people's experiences in place contributes to a deeper understanding of the processes of individualization, inequality, and of generation." Being able to take a closer looks at youth cultures and subcultures in different times and places adds an extra element to understanding the everyday lives of youth. This allows a better understanding of youth and the way generation and place play in their development. It is not where the birth cohort boundaries are drawn that is important, but how individuals and societies interpret the boundaries and how divisions may shape processes and outcomes. However, the practice of categorizing age cohorts is useful to researchers for the purpose of constructing boundaries in their work.