Nielsen: Online Video Viewing Declines (Slightly) in December

Mark it up to the holidays, maybe, but online video viewing declined last month, with the number of online video views falling about 4 percent from November to December and viewership declining at four of the top five video properties, according to new data from Nielsen VideoCensus.

Despite the monthly decline, the year-over-year picture is a little brighter, with unique viewers, number of streams, and time spent watching online videos each up over 10 percent from the previous year. Unique viewers grew 10.3 percent, to 137.4 million in December, with total streams at about 10.7 billion. The amount of time spent watching videos online was also up year-over-year, to 193.2 minutes per month, on average.

Four of the top five video properties in November saw declines over the following month. YouTube‘s (s GOOG) streams were down from 6.7 billion streams in November to 6.4 billion in December, while the number of streams also declined at Hulu (from 657 million to 635 million), MSN (s MSFT) (from 147 million to 141 million), and Fox Interactive Media (s NWS) (from 137 million to 125 million).

No. 3-ranked Yahoo (s YHOO) proved to be an exception among the top five, growing from 197 million streams to 244 million streams month-over-month. Meanwhile, Turner Sports bounded into the top 10 — and all the way into the top five — with 142 million streams during the month.

Of course, not everyone believes Nielsen’s estimates, and some video companies — like Hulu — have expressed frustration over the research firm’s methods for determining the unique users or streams viewed. Nielsen is trying to change that, with a new initiative to install “Internet meters” in homes that participate in its National Television Panel.