Well, not sure about 1971, but in early '70, I was living in Midwest City after military service and a few months time. One job was at 5-cents above minimum wage, which was $1.60 at the time.
As for the charts, even at my age then (born 1946), I wasn't keen on what trends were at the time. I was just trying to make a living and support a wife and 1 kid at the time.
I've seen similar charts referenced in some of Buchanan's ad others' work on cost of living and the decline of Western Society.
In 1970 most of the kids I knew were lower middle class, working families. Which in 1970 meant Dad worked, Mom stayed home. Not universally true, but it was the norm. We peaked, then from 71 on it's pretty plain that wages relative to costs stagnated.
How many working-class guys can support the family while Mom stays home today? We destroyed our culture in the 20th century - put women in factories, ruined our public schools, detached our currency, and selected "entertained" rather than educated.