YouTube is following in the footsteps of Google and has officially changed their algorithm when it comes time to rank videos. YouTube Algorithm Changes Explained
There was really one big difference that we saw with the update: clicks are less important. This goes for both the video as well as the ads connected to the video:
Time is more important for content. In the past YouTube focused heavily on the number of clicks a video received. The problem with this was the fact that videos with catchy headlines were getting all of the attention. Now, YouTube is focusing more on the time that someone spends watching the video.
Time is more important for ads. Not only is the time a user watches a video more important than simple clicks, but this same logic also goes for advertisements. If you want your video to rank higher, people will have to sit through those ads.
Via Ileane Smith