Nielsen has unveiled the VideoCensus tool to measure online video viewing, with the capability of slicing and dicing the data by home and business use, and by audience size, demographic, location and the time spent watching.

For advertisers, understanding online video audiences with a deeper degree of granularity will help their targeted and interactive advertising efforts. Unilever, Marks & Spencer and Yahoo! have all endorsed the approach.

VideoCensus, Nielsen said, will help advertisers hone in on specific desireable demographics by offering information about the types of sites and genres that individual age groups prefer, along with the average times of day they watch the most video.

Nielsen has released its first set of data points from VideoCensus in the U.K., finding that men view 78% more online video than women. Out of the top 10 online video sites, only two--ITV and Channel 4--had more female eyeballs. YouTube is the highest ranked site overall, and 26.9 million people in the U.K. streamed online video in April 2011.