Google introduced a “YouTube video speed dashboard” to give you insight into what your YouTube speed looks like compared to the YouTube speed of users in other regions and different ISPs. YouTube video speed depends on many different factors ‘your Internet connection, ISP you’re using and distance to video servers.’ “The speed numbers are calculated by measuring speed at which YouTube video is received by the browser. This is then averaged over the previous 30 days provided you've used the same browser during this time period. A higher YouTube video speed translates to a better and faster experience not just for YouTube videos but for the Web in general; and by making this speed data available to users we would like to continue our ongoing efforts to make the web faster,” revealed.
More info: YouTube Video Speed Dashboard