Perhaps owing to similar reasons that have led to a strong summer for cable network ratings, according to both Nielsen Online and comScore new highs have recently been set in the online video market. According to Nielsen, a record audience of almost 136 million viewers watched video online during the month of July, up 14.2% year-over-year. ComScore measured a larger audience of 158.4 million viewers for the month of July, an increase of 11.8 % over comScore’s measurement in May 2008.

At the beginning of this summer there was a debate concerning online video measurement and Hulu’s traffic; I compared the numbers for Hulu in a July posting. Based on the latest numbers, Nielsen and comScore differ about 16% in regards to the U.S. online video audience (total unique users). This is probably attributable to some difference in their research methodology, which is unclear since they both seem to use panel based projections combined with server data for validation purposes. Nielsen promotes that they were the first to market and that their panel as being “truly random,” being assembled from two separate samples of 200,000 members, 20,000 of which are selected for a “more scientific” panel through their “street addresses and phone numbers.” Nielsen also stresses that their panel “includes both heavy and light users” and that “other measurement companies create their panels from people who answer online solicitation and who tend to be heavy users.” For their part, comScore highlights that their panel is composed of 1 million users for the U.S. market, and that it has been “validated by several leading industry bodies and the use of independent third-party data sources.”

In any case looking at the measurements available for the past two years for the U.S. online video audience it seems that the firms are arriving at more common assessment.

However in terms of total video streams, there seems to be a larger and widening gap.

This larger difference, relating to the amount of video watched rather than audience size, indicates that the panels probably weigh differently in terms of heavy video users. This doesn’t solve the problem however since it is impossible for me to say which panel is too heavy, or too light. Nielsen and comScore are probably comparing these figures to the server data and arriving at different perspectives of what the correct market weight is.

Since comScore breaks out minutes of video consumption per user for Hulu, YouTube and MySpace tomorrow I will be looking at those figures and posting up a comparison.