The January numbers from Nielson Media Research indicate that CNBC is seeing deterioration in its ratings compared to the year ago period. Furthermore, the losses are concentrated in the key 25-54 age demographic. The ratings slide could cause changes as Comcast executives review their new NBCU properties. While declines can be witnessed across the board, Maria Bartiromo's time slot on "The Closing Bell" was among the hardest hit. Viewership was down 22% in January from the year ago period for the 3-4 p.m. EST time slot and a whopping 36% for the 4-5 p.m. EST time slot for the 25-54 demographic. When comparing the most recent week, where Maria Bartiromo was covering the World Economic Forum from Davos, Switzerland, to her coverage last year, viewership has fallen 43% for the 3-4 p.m. time slot in the key demographic and 47% for the 4-5 p.m. segment of "The Closing Bell." The network as a whole lost 13% of its 25-54 demographic in January 2011 compared to January 2010. Another segment that has seen a contraction in the 25-54 demo is the 12-1 p.m. hour where the network is now broadcasting the "Fast Money Halftime Show" and the "Strategy Session." Last year, this hour of programming was dedicated to "Power Lunch." Viewership for this hour is down 31% year over year for the 25-54 demo. The other very noticeable decliner was the 11 a.m. - 12 p.m. "The Call" segment which lost 35% between January 2010 and January 2011 in the 25-54 demo. It will be interesting to see how Comcast (NASDAQ:CMSCA) execs approach these numbers as the company takes over ownership of the property from General Electric (NYSE: