According to the website TVNEWSER, Fox has 1,761,000 viewers for all day, and 1,097,000 in primetime. But only a very small part of those viewers are in the 25 to 54 age group -- 16.69% for all day and 20.23% for primetime. That means that 83.31% of all day viewers and 79.77% of primetime viewers are not in that prime demographic -- and almost all of them are over 54 years old. In fact, the average age of a Fox News viewer is now 65 years old.
Those are very bad numbers for Fox News, and predict a bleak future for the network. As their old viewers die off, there are not sufficient numbers of young viewers to replace them -- which means the ratings will continue to drop (until their numbers are even worse than CNN's). And the numbers in the 25 to 54 age bracket keep falling for Fox (indicating that their efforts to stop the bleeding are not working).
In 2013, viewers in that demographic dropped by 19% for the total day viewing. For primetime, it was even worse with a drop of 30%. And that was evident in all the primetime shows -- with Hannity showing a 16% drop, while Kelly and O'Reilly dropped 23%.
Younger viewers just don't like the far-right-wing political bent of Fox News. They are much more tolerant of the LGBT community, immigrants, minorities, and women, and believe the rights of those groups must be protected. They just don't like the hate toward those groups being spewed forth by Fox News. That is very good for this country as a whole, but it is very bad for Fox news.