Every time a TV personality migrates to streaming, the tricky business of audience measurement rears its head. Here’s a rundown of the basics. When Fox News and its top-rated personality parted ways last month, it was immediately unclear what either planned to do next. Fox News subsequently saw its viewer numbers drop nearly in half during Tucker Carlson’s former time slot—from an average of more than 3 million to an average of around 1.65 million, according to reporting from the Washington Post.