Here are the ratings that have Viacom execs worried about their ailing TV networks

Here's a snapshot of just the last full quarter of primetime ratings available to us from Nielsen. This gives us a sense of which Viacom networks have the biggest total audience currently.

Top 3
1. Nick-At-Nite – 962,000
2. Spike TV – 725,000
3. VH1 – 660,000

Bottom 3
1. CMT – 287,000
2. MTV – 454,000
3. TV Land – 513,000

Usually, most cable networks sell ads for the higher age bracket of 25-to-54-year-olds. But taking into account the younger viewership of many of Viacom's cable networks, we decided to compare them at the 18-to-49-year-old demographic most often used by the broadcast networks.

These numbers give us a sense of which networks are hitting broad, advertising-friendly audiences.

Top 3
1. VH1 – 419,000
2. Comedy Central – 375,000
3. Spike TV – 354,000

Bottom 3
1. CMT – 125,000
2. TV Land – 154,000
3. MTV – 292,000

In order to see how the channels are doing with young people, we combined the average primetime viewership for the 2-to-11-year-old and 12-to-17-year-old demographics. One would expect that MTV and Nick would rank highest with these young viewers, but that's not quite how it works out.

Here's how it looks:

Top 3
1. Nick-At-Nite – 541,000
2. VH1 – 102,000
3. MTV – 97,000

Interestingly, VH1 just edges out MTV with young viewers, even though VH1 had always been positioned as capturing audiences who age out of MTV's youth demo and into the adult demos.

Note: Nielsen doesn't measure CMT and TV Land in these younger demos, so they aren't included in this report.