YouTube ads running around music videos are a growing revenue stream for a number of labels and artists, but how many people actually watch them – especially when they’re skippable? At yesterday’s Online Video Advertising Summit, YouTube dodged the question – “It varies” was head of video strategy Kathryn Friedrich’s answer according to Tubefilter. However, video advertising firm TubeMogul gave an answer: 15%-25% of skippable videos are watched in full. Separately, there’s a new report on how fast (or slowly) TV ad dollars will move to online video. PwC’s latest media report claims that online video advertising will be a $5.9bn business by 2017, up from $2.3bn in 2012. However, TV ads and sponsorships will still be generating $81.6bn in 2017. PwC suggests that one thing slowing down online video ad-spend growth is the challenges brands and agencies see in accurately measuring how effective those ads have been. Which, in theory, is one thing that skippable video ads help to solve, since the 15%-25% of ads that are watched in full are generating real engagement.