This data is not beautiful. What’s the cause? Seems odd, affecting both students and adults, so it’s like knowledge decay as well as poorer uptake of knowledge. Social media and device usage?

Not discounting knowledge decay, but fwiw it could be interpreted as the poorly-scoring teenagers who become adults lowering the average, which builds up year by year as their portion of adults steadily increases and the higher-scoring adults die off, rather than the individual adults scoring lower every year. Could totally be existing adults continuing to score lower as years pass, though.

Haven’t looked into the study, just adding my two cents on the graphic.