https://www.theguardian.com/technology/2019/aug/27/youtube-to-adjust-uk-algorithm-to-cut-false-and-extremist-content

Views via recommendations of such ‘borderline’ videos were halved in similar US trial

YouTube is experimenting with an algorithm change to reduce the spread of what it calls “borderline content” in the UK, after a similar trial in the US resulted in a substantial drop in views.