I don't know, feels like a paper titled "Is Google Getting Worse" could have benefited from actually looking at Google results rather than only results of other search engines.
Edit: This got downvoted to hell, so let me be more explicit. This study did not look at Google results, the title is pure clickbait. They used Startpage results as a proxy for Google results. I don't think that's a valid assumption, even if Startpage is using Google's index.
Edit: This got downvoted to hell, so let me be more explicit. This study did not look at Google results, the title is pure clickbait. They used Startpage results as a proxy for Google results. I don't think that's a valid assumption, even if Startpage is using Google's index.