For young adults at least, often it is Univision, the Spanish-language broadcaster. And yes I mean in the United States. On nineteen different nights (since September), Univision has ranked number one among 18 to 34 year olds. Two-thirds of the time Univision has made it into the "big four" (the three networks plus Fox) with this age group.
The information is from The Wall Street Journal, 2 May 2005.