xiggi the point of your original post was that in your “conclusion? Relying on ACT scores only might be no longer be such a wise idea!”
as roman is pointing out the overall mean ACT hasn’t changed much over time and it corresponds pretty well with the mean SAT. There will always be some level of variance between what a student will score on the SAT vs the ACT per roman’s sports analogy which explains the .92 coefficient between SAT and ACT.
However, looking past your belief via your cherry picked anecdotal evidence that the concordance tables are not very accurate, if you check out the 50-75% SAT and the ACT scores of any university, the range values are pretty true to the concordance tables as the high correlation coefficient would suggest.
I understand that you are CC resident guru of SAT prep so that may be clouding you view of the ACT but that is no reason discourage the use of the ACT.