Boomers. Millennials. Gen Z. We hear those terms more and more to describe people of certain ages.

But who exactly falls into what category and who decided that anyway?

According to the research firm the Center for Generational Kinetics, a generation is a group of people born around the same time and generally in the same area. As such, they tend to exhibit similar characteristics, preferences and values over their lifetimes, the center explained, typically because they experienced similar trends at the same point in their lives.

There are slight variations in the definitions of a specific “generation,” but research from USC Libraries points to the following as the general guidelines for each group:

• The Greatest Generation – born 1901-1924.
• The Silent Generation – born 1925-1945.
• The Baby Boomer Generation – born 1946-1964.
• Generation X – born 1965-1979.
• Millennials – born 1980-1994.
• Generation Z – born 1995-2012.
• Gen Alpha – born 2013 – 2025

Generational cutoff isn’t an exact science and isn’t always linked to a certain span of time, as Pew Research explained. And, for all their bad press, there’s only one generation officially designated by the U.S. Census Bureau, which recognizes Baby Boomers based on the surge of post-World-War II births and a decline in the birth rate after 1964.