The Strauss–Howe generational theory, devised by William Strauss and Neil Howe, describes a theorized recurring generation cycle in American history and Western history. According to the theory, historical events are associated with recurring generational personas (archetypes). Each generational persona unleashes a new era (called a turning) lasting around 20–25 years, in which a new social, political, and economic climate (mood) exists.
An average life is 80 years and consists of four periods of ~20–22 years
Childhood → Young adult → Midlife → Elderhood
A generation is an aggregate of people born every ~20–22 years
Baby Boomers → Gen X → Millennials → Homelanders
Each generation experiences "four turnings" every ~80–90 years
High → Awakening → Unraveling → Crisis
A generation is considered "dominant" or "recessive" according to the turning experienced as young adults. But as a youth generation comes of age and defines its collective persona an opposing generational archetype is in its midlife peak of power.
Dominant: independent behavior + attitudes in defining an era
Recessive: dependent role in defining an era
https://en.wikipedia.org/wiki/Strauss%E2%80%93Howe_generational_theory