Eli5: why are there different generation band lengths?

Question

From my understanding each generation should be 18 years

Boomer: 1945-1963
Gen x : 1963-1981
Gen y: 1981-1999
Gen a: 1999-2017

However I see on a lot of sites people have the Gen x range to be 20 years and Gen y to be 15

In: Biology

Answer 1

Generations are defined by shared common experiences, typically during the ages of ~10-20. Depending on the experiences and the state of the world, different cohorts of ages are going to have different formative experiences. The reason that generations are often different band lengths is because of how those experiences affect different ages. Like, I’m a millennial – some of our common, shared experiences are things like: 9/11 [this is probably the biggest one], the emerging prevalence of home computers and internet, personal cell phones becoming common, the politics of GWB (when we were teenagers) and the election of Barack Obama (who we voted for), the 2008 financial crisis, etc. Gen X would’ve been well into adulthood by the time these things happened, and were fairly instrumental in *making* those things happen. By the same token, millennials weren’t nearly as shaped by things that shaped Gen X – the fall of the soviet union, the Presidency of Reagan, the economic boom of the 1980’s.

Given that historic events don’t happen on a strict and uniform timetable, the types of events that affect whether birth years feel “similar” enough to be part of a generation or not may make it so that some generations feel like they last longer than others. It’s also why there are always cusp years, where people born in those years will often feel like they belong to both, or neither, group (because they kind do). Millennials, I think, are strongly shaped by the years from ~1999 to ~2009. The events that came before and after those years feel dramatically different. Boomers, I think, are strongly shaped by 1960-1974 (basically JFK through Watergate). Note that’s a 40% longer time period, but (at least to me) the events both before and after those things feel dramatically different.

It’s also why generations aren’t cross-cultural. The generations in the US don’t translate to, say, middle eastern generations, or chinese generations.