As readers know, The Baby Boom describes post-WW11 elevated U.S. birth rates. (Other countries also experienced increases.)
What surprises many is the number of years the spike lasted - from 1946 to 1964, according to the U.S. Census Bureau. Thus, people born during those years are referred to as Baby Boomers.
To address the significant 18-year span, I separate Baby Boomers into three sub-groups: First-wave, Midpoint, and Last-wave.