Baby boomers are the postwar bulge in birthrates that lasted roughly 20 years. It is generally accepted that it runs from 1946 to 1966. I haven’t looked deeply enough at his numbers, but if he is sloppy it isn’t in his definition of boomers.
Demographers place the “boomer” years as 1946 to 1964, because the birthrate dropped below 4 million/year after ‘64.
Politically, I (personally) group them differently. The boomers who were of draft age (18) before the end of the draft are politically and philosophically very different than the boomers who are at the tail end of the boom (eg, 60 to ‘64). Most people I know who were born in the 60’s look and listen to the “protest era boomers” and wonder “WTF? When will these clowns get *over* themselves?”
The people born between ‘45 and ‘55 are, without a doubt, some of the most self-obsessed humans to have ever walked the planet.