GMAT Sentence Correction (SC) | Soaring television costs accounted for more than half the

Hi All,

Soaring television costs accounted for more than half the spending in the presidential campaign of 1992,a greater proportion than it was in any previous election.

Let’s begin with understanding themeaning of this sentence . The sentence says that increasing television costs were responsible for more than half the spending in the presidential campaign of 1992. This proportion was greater than any proportion in any previous election.

Now let’s begin the erroranalysis:
There are a few singular entities that “it” may refer to. These entities are “spending” and “the presidential campaign of 1992”. However, none of these entities are logical antecedent of “it”. Hence, presence of this pronoun makes this sentence incorrect.