• by Daisy Whitney , Op-Ed Contributor, January 20, 2012

The number of video ads served by the top online video ad properties in the U.S. in December rose 20% compared to the same period a year ago. In December 2011, about 7.1 billion video ads were served across the biggest video ad properties, up from 5.9 billion for the same period a year ago, according to an analysis of comScore’s most recent online video rankings. The frequency of ads delivered rose slightly to 46 ads per viewer in December 2011, for a 15% boost compared to a year ago.

Hulu still topped the list in ads served at about 1.5 billion, a 22% jump. After Hulu, the top five list included Adap.tv, Tremor Video, Brightroll and Specific Media. Across the top five online video ad properties, the number of video ads total grew about 25% to 4.9 billon in December 2011 compared to the same time period a year ago.

In terms of scope, the leading online video ad properties reached about 51.4% of the U.S. population, about on par with the reach a year ago of 49.1%.

Interestingly, comsScore also found that video ads in December 2011 comprised 14.1% of all videos viewed and 1.2% of all minutes spent watching online video, a slight dip from December 2010 when video ads accounted for 16.4% of all videos viewed and 1.6% of minutes.