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Research conducted by PLYmedia shows that subtitles in online videos increase the the amount of time a user spends watching them by 40%. Furthermore, in a comparison between subtitled videos to identical videos without subtitles, PLYmedia found that the videos with subtitles were watched 91% to completion, compared with 66% to completion for those without subtitles.

As a post at ReelSEO notes, "This is an important indicator for post-roll video advertising as well as for those videos that have a branding message or call to action at the end of the video."

eMarketer says that $6 billion will be spent in the US a year by 2013. There is expected to be tremendous growth each year before that:

So why do the subtitles have such a huge impact? Certainly this helps in cases where the viewer is hearing impaired or speaks a different language from what the audio is presented in, but eMarkter notes that most of the targets of B2B marketers are in their office most of the day without their sound turned on.

Not a bad point to consider. eMarketer says viewing of videos on mute is expanded 20-fold with the addition of subtitles.

For those already in the online video game, these probably aren't statistics that should be ignored. If nothing else, subtitles make your videos more accessible. A way to turn them on/off is probably the best way to go, because many people would still prefer to view their videos without any added clutter on the screen.