To correlate the effect with social processes, one would have to plot the same graph for multiple countries and see what processes occur in each history at the time of the lines forking apart (assuming they do so).
Some guesses: automation, perhaps globalization of supply chains, something related to the effectiveness of employees at bargaining with employers?
Does anyone know what happened in the early 1960’s that led to that smaller, but still noticeable diversion?
MBAs took over businesses from internal promotions.
Unfortunately I don’t know.
To correlate the effect with social processes, one would have to plot the same graph for multiple countries and see what processes occur in each history at the time of the lines forking apart (assuming they do so).
Some guesses: automation, perhaps globalization of supply chains, something related to the effectiveness of employees at bargaining with employers?