How many people make up 1.0 Cable TV Rating.?

That's going to vary depending on where the measurement is taken. The measurements are based on a "universe" which is all viewers in a market area called a DMA. (List of DMAs: http://www.tvb.org/research/measurement/131627 ) National ratings are based on a universe that includes the entire US. A rating of 1.0 is 1% of all the viewers in the measurement universe.

So, let's compare DMA #1 - New York to DMA #81 - Madison, WI

NY Universe = 7,368,320 so 1% = 73,683 viewers

Madison Universe = 374,980 so 1% = 3,749 viewers

To get a really accurate picture, one must also look at the "share". The share is the percentage of the actual viewers using TV at that time.

For instance, if a show at 2 am had a 2.0 rating and a 50% share, that means they only had a total of 2% of the viewers in the measurement universe watching, but that was half of those awake and watching TV at the moment (so, only 4% of the total measurement universe viewers were using TV at that time). That's pretty popular for 2 am.

At 5 pm a show could have a 2 rating and a 3 share meaning 97% of the viewers were watching something else. It's the same 2 rating so the same number of viewers but the share shows those numbers suck.