1. 2008PopularityOne big Trending page ranked by views, the same for everyone.
2. 2011ClicksYouTube learns that a click does not mean the video was watched.
3. Mar 2012Watch timeRelated and Recommended videos shift to time watched.views −20% at once
4. Oct 2012Search tooSearch ranking starts rewarding videos that keep viewers watching.
5. LaterValued watch time1 to 5 star surveys; only 4 and 5 stars count as valued.