Yes, but that’s not the relevant datum, because of selection effects. The relevant question is how well employed is the person who had a choice to do a Ph.D. or not compared to the counterfactual person who made an opposite choice.
As an example, an Ivy graduate makes more than state school graduate on average, but there was a study showing that those offered Ivy admission but deciding to go to a state school made just as much (that study setup has its own selection bias issues, but hopefully those gives an idea of what I mean).
As an example, an Ivy graduate makes more than state school graduate on average, but there was a study showing that those offered Ivy admission but deciding to go to a state school made just as much (that study setup has its own selection bias issues, but hopefully those gives an idea of what I mean).