Last week, in the opening week of the current prime-time season, Mr. Leno's margin of victory over Mr. Letterman was the closest the two shows had been in terms of viewers - 5.5 million for NBC versus 4.96 million for CBS - since 1994. And in the category that NBC and advertisers most prize, adults between the ages of 18 and 49, the margin was the closest for the two shows since 1996.
Q : There are two clauses connected into one sentence without a conjunction.
"Last week,.......the closest + the two shows....-since 1994."
What kind of a relationship between them is? I think the clause "the two shows.....since 1994" functions as an adverb, showing a kind of information about a ground of the writer's thought that the gap of a number of the viewers is the closest. What do you think?
All the best,