the viewers give tv shows their ratings. anyone can infact,
Nielsen Ratings
Networks know how many people watch tv shows, such as Friends, by the Nielsen Ratings. The Nielsen Ratings let television companies know what shows are being watched and how popular they are.
The Best TV Shows That Never Were - 2004 TV is rated/received certificates of: USA:TV-PG
it gives some enjoyment and entertainments.
Songs uit de shows - 1966 TV is rated/received certificates of: Belgium:KT
The Best of Aussie Cop Shows - 2002 TV is rated/received certificates of: Australia:PG
Nielsen rating
In America at least, you need to have a Nielsen box which records what shows you watch. The average person's viewing habits really have no effect on the ratings on TV shows. I have read that somehow ratings are tallied from DVR playbacks but I haven't the foggiest how that happens as I don't own a DVR.
As of 2013: NCIS, The Big Bang Theory, The Voice
There are numerous sources one can access if wanting to locate rating reviews on children's shows. Depending on specifics ( whether it is a TV Show, or ratings for a children's Theatre Production) there are several sources available. For TV Shows, Commonsense Media offers reviews and ratings in this area, or alternatively one can locate ratings within high profile news media publications, such as The Guardian, or Time Out.
An excellent website for TV listings is www.zap2it.com. Not only does it give the time shows will be aired on television, but also ratings on specific shows to help ambivalent viewers select entertaining shows.
While many websites will give reviews of different television shows, there is only one good website. The best website by far for TV ratings is www.nielson.com.