Generational cohort theory

Intellectual roots

Karl Mannheim's essay on the problem of generations argued that a generation is more than an age group: it is a set of people positioned to experience history in a common way. Ronald Inglehart later proposed that those raised in material security prioritize self-expression and quality of life more than those raised amid scarcity. Popular labels such as Boomer and Millennial draw loosely on these ideas.

The identification problem

Finding true generational effects is harder than it appears. Three influences are bound together, since a person's age equals the survey year minus birth year.

• Age effects: changes that come with getting older
• Period effects: events that affect everyone at the same time
• Cohort effects: lasting differences linked to when people were born

How much evidence is there?

A one-time comparison of older and younger workers cannot separate these influences. A meta-analysis by David Costanza and colleagues found that generational differences in work attitudes were small and inconsistent, and a 2020 report by the US National Academies concluded that generational categories are of limited use for workforce management. Boundaries between named generations are arbitrary, and variation within a cohort is large. Cohort differences do appear in some long-running data, but widespread claims about the distinct traits of each generation go well beyond what the evidence supports.