In 1970, the average ACT scores was about an 18. Now it's like a 21. So its about three points higher. If you got a 28 on your ACT in 1970, it would be the equivalent of having a 31 on your ACT now.
Yes actually;
there are several websites out there, but I'll help the best I can:
(Note: these are all "ish" and relative values for IQ/SAT/ACT scores so give or take some)
CLASS | SAT | ACT | IQ...