Social media AND smartphones became popular around that time. I think it's the toxic combination that's the worst - easy, low effort dopamine hits that are available everywhere via your phone, whenever you are bored.

In 2013 social media was still a textual medium, right? There was Vine, but that died pretty quickly, from what I remember.

If social media and smartphones are the problem, I would have expected that results for English proficiency would be steady until the advent of TikTok, right?

From 2011 to 2013 smartphone adoption in the US went from 35 to 55%, and by 2016 was 75%. While not proof of causation, the correlation is very strong.

Pfft, it started in 2007. Kids couldn’t deal with the orange box, cod4, halo3, all coming out at once.

Actually, it is a good point that this is a lagging indicator.