I decided to compare old versus new wages using the inflation calculator, link below. Regarding the person earning $4.75 in 1971, it would now be $29.42. Not quite over $40, but not bad either. I also was working as a supermarket checker in 1956. First as a union employee they paid me $1.40 per hour or $12.60 today, then they discovered I was leaving for college after the summer and cut me to $1.05 or $9.45 today. Somewhere between 1956 and 1971, it appears that workers started to be paid better.
https://data.bls.gov/cgi-bin/cpicalc.pl?cost1=4.75&year1=197101&year2=201712
Surely you don’t take those government figures seriously, they are laughable.