This week Sony announced that it would acquire video sharing site Grouper for $65 million. While Grouper’s market share of visits is only 1/144 that of YouTube’s in the US, it ranks among the 15 most visited video sharing websites, and its traffic has increased substantially over the past six months, as you can see from the chart below.

Hitwise clickstream data shows that Grouper’s leading source of traffic is Yahoo! Video, which accounted for 41.65% of its US traffic for the week ending 8/19/06. I was curious to see how Yahoo! Video affected Grouper’s growth, so with our new clickstream charting feature that launched this week, I charted the downstream from Yahoo! Video to Grouper over the same time period, and found an almost exact correlation between Grouper’s market share of visits and how much traffic Yahoo! Video was sending it:

In comparing the two charts, we see how important that 3-5% of Yahoo! Video’s downstream is to Grouper. Sony has said that it acquired Grouper for its technology rather than its traffic, which makes sense given that Grouper has been so dependent on a single source of traffic. Clickstream information such as this can be a very valuable tool in determinig sources of traffic and evaluating the success of online partnerships.