I would like a study that presents all this graphs (separately) to people and have them choose the inflection point. They would not all be on 1971. Some are very clearly a different year or just a gradual change.

The adding of arrows biases people to say everything happened in 1971 exactly.

I think there was a shift in national priorities and attitudes - roughly late 60s to early 80s. But, this bias is tricking people into thinking that one particular event was the cause of this shift.