How do companies know how many veiwers a particular proggrame had?
Also while am at it, why has that lovely old british word disappeared, "films" & been replaced by awfull "movie"

A research firm installs recording devices on televisions in a small percentage of households. The devices transmit information about which channels are viewed back to the research firm. Further data is obtained from families that maintain a viewing diary for a token fee. See Nielsen Media Research and ACNielsen - Wikipedia, the free encyclopedia

I think "films" might apply to a broader range of media than the dramatic form most associate with the term "movies". There's also a remnant of Americans wanting to feel separate from the UK as in spelling differences like color/colour and how to pronounce aluminum and tomato. Sometimes those American forms get picked up on the East side of the Atlantic.