Yep, people completely get confused about "cohort" vs "age".
"Cohort" is the year you are born. This might make you a Baby Boomer, X, Y, Z, ... You keep your cohort throughout your life.
The cohort who got physics PhD's prior to 1968 got jobs in the field easily (e.g. most were good at physics, it didn't matter how good you were at musical chairs); after 1968 the job situation changed (you certainly were good at music chairs.) This is a function of when you were born.
"Cohort" is the year you are born. This might make you a Baby Boomer, X, Y, Z, ... You keep your cohort throughout your life.
The cohort who got physics PhD's prior to 1968 got jobs in the field easily (e.g. most were good at physics, it didn't matter how good you were at musical chairs); after 1968 the job situation changed (you certainly were good at music chairs.) This is a function of when you were born.