Hoeflin writes:

It is most remarkable that Hoeflin got data on the combined SATs of all FIVE MILLION people who took the SAT from 1984 to 1988. I wonder how he was able to get it. This makes the Mega Test potentially the best normed test of all time.

Hoeflin continues:

How did he arrive at 15 million 18-year-olds from 1984 to 1988? According to a USA Today article published June 12th, 2020:

YearNumber of babies born in the U.S.
19663,606,274
19673,520,959
19683,501,564
19693,600,206
19703,731,386

That’s a grand total of 17,960,389 babies born from 1966 to 1970. Of course not all of these babies would have lived long enough to be 18 from 1984 to 1988. According to an article in the Chicago Tribune , about 10% of Americans born 1966 to 1970 were dead by 2021. Even if we absurdly assume, all of them died before 1984 to 1988, that would still leave 16,164,350 alive by those years. Perhaps about a million emigrated, but I suspect they would have been more than replaced by all the kids who immigrated.

I realize Hoeflin may have rounded down to 15 million for simplicity and this my not ave affected the IQs he assigned all that much, but when you create the Mega test; Mega for million because he wanted to identify scores with one in a million rarity, it helps if his denominator is not off by a million.