That graph is from the new book by political scientists Pippa Norris and Ronald Inglehart (2019), Cultural Backlash: Trump, Brexit, and Authoritarian Populism.
Just finishing the book now. I'd call it a rigorous validation of the conventional wisdom of the moment. Certainly required reading for anyone with weirder theories about the culture wars. This will probably serve as the baseline model for some time.
Our theory argues that a cultural silent revolution has heightened polarization over cultural issues in the electorate, provoking an authoritarian backlash among social conservatives. We hypothesize that socially liberal values are spreading through intergenerational population replacement and demographic shifts, causing traditionalists (concentrated among the less-educated and older birth cohorts) to feel threatened, perceiving that respect for their core values and social mores is rapidly eroding. These developments have cumulated over time to reach a tipping point in high-income Western societies…
If you read between the lines there are some more tantalizing insights, such as the one dramatized in the graph above. I would like to write a longer review, but we'll see.
Patrons may have noticed this in my hard drive a week or two ago.