> On Facebook, there is 100% difference between the top 20 headline phrases in 2017 vs 2019/20... We can attribute this stark change to a few things; algorithmic maturity, audience preference and the publisher landscape.
Or that means you're measuring the completely wrong things about headline authoring, because the data have no stationarity at all.
They allude to this, but it would appear that the only thing that matters is Facebook's editorial, laundered through an algorithm. So maybe a more valuable article would be hacking into Facebook and just finding out what it is they idiosyncratically value in a headline.