• by Tyler Loechner  @mp_tyler, May 5, 2014

The amount of pre-roll video ad slots available through supply-side platforms (SSPs) and programmatic ad exchanges increased 63% in Q1 2014 compared to Q4 2013.

The data comes form TubeMogul’s latest U.S. online video advertising update, which includes data from October 2013 through March 2014.

TubeMogul notes that inventory available for real-time bidding (RTB) from “Tier 1” publishers and comScore Top 100 sites increased by 110% and 78%, respectively, in Q1 compared to Q4. The company writes in the report that this demonstrates “that the most premium inventory channels are the fastest growing.” That is partly attributable to the fact “premium” publishers have held back from exchanges longer than others, making it easier for them to have high-growth figures on a quarter-over-quarter basis.

TubeMogul says CPMs for pre-roll inventory in the U.S. was $8.04 in Q1 2014, down just 2% from Q4 2013. Interestingly, CPMs in March exceeded CPMs in December, which TubeMogul notes is traditionally the most expensive month. March’s CPM average was $8.86, while December’s was $8.42. We have to wait for future data to see if March’s spike in cost is the start of something new or if it will ultimately become an anomaly.

Private marketplace activity is up big so far in 2014, too. TubeMogul says there were 191% more private marketplace deals in Q1 compared to Q4. The company claims private marketplaces (ones using TubeMogul’s BrandAccess service) are nearing the two billion impressions per month mark.

Perhaps one reason private marketplaces are taking off is because they can lay claim to significantly higher viewability rates. TubeMogul says inventory bought through private marketplaces averaged 55% viewability, while overall viewability averaged 29% in Q1.

There is still plenty of room for improvement in both categories, but the industry is at least headed in the right direction -- in Q4 the viewability rates were 49% for private marketplace deals and 23% overall.