50% of viewers will generally leave your video within the first 10 seconds. This is because (generally) half of the people clicking on a video will decide it isn’t for them by the time you give the “hook” for a video.

Roughly 25 to 40% of viewers will remain until half of a very good video. This is a natural thing that seems to occur because the video is just longer than the person’s attention span, the viewer gets bored with the content, or they move to another video that may be more related to what they were searching for.

The real answer to this question resides in how many people make ti to the end of the video. As far as my channel is concerned, 10% is a high retention rate with 5% as my goal for this stage of my video. Channels with higher retention rates tend to do better in terms of YouTube algorithm sorting, which in turn allows them to grow faster.