YouTube new Video Ranking Factor Time Watched Video Optimization for Time Watched

Now in YouTube analytics all YouTube videos will be ranked including their viewers engagement time factor.
As YouTube says about it's new ranking as..

  The experimental results of this change have proven positive -- less clicking, more watching. We expect the amount of time viewers spend watching videos from search and across the site to increase.  As with previous optimisations to our discovery features, this should benefit your channel if your videos drive more viewing time across YouTube.  

The main reason to add the time ranking factor is only due to YouTube lastly made the changes for thier  ongoing efforts to focus their video discovery features on watch time, and follows changes that they made to Suggested Videos in March, and recent improvements to YouTube Analytics.

Now your all videos getting ranked higher depending upon for how much time they watched instead of counting the total clicks for a video.On October 11,2012 YouTube added new Time Watched reporting to YouTube Analytics, due to which it becomes easy for you to check the YouTube analytics performance of your videos and channel by using more YouTube tools. there for video produces should optimised their videos as for their fans that they love and share, and encourage them to discover more of what YouTube offers, and you’ll see your own fan base grow, too