when somebody says a tv show got 5 million viewers, is this an actual fact or an estimate? this wikipedia article is all i could find on the topic.

http://en.wikipedia.org/wiki/Broadcaster%27s_Audience_Research_Board

it says that there are only 5,100 homes participating in a survey by using a box linked to their telly. and this is how all the ratings for the uk are gathered.

does this not strike you as a little ineffectual? i know statistics can be representative bladdebla sample size accurate enough etc. but is it not strange that these 5000 people effectively decide what we watch on tv. if they watch it, the producers show more of it so the rest of us have to watch it too.

another issue: when they say 'ratings increased by 1 million' (like on big brother recently) and they're just extrapolating a figure from the sample, how do they know how many people were watching tv at that point countrywide?

obvs i know you dont care about who comes top of the ratings pile, but doesnt this system seem prone to misrepresentation? and everything we watch is based on it