A Practical and Authoritative Guide to Contemporary English. 1996.
Page 55
In this sentence the condition of the new buildings is compared with the old buildings themselves, not with their condition. To make the sentence parallel, you must add the pronoun that to balance the noun condition. Again, you can repeat the noun if this is more to your liking, but in either case the prepositional phrase with of must follow:
They felt that the condition of the new buildings was not much better than that (or the condition) of the old ones.
1
Sometimes it’s only the second preposition that gets left out in these comparative constructions, as in More cars are built in Canada than Mexico, where perfect parallelism requires … than in Mexico.
2
As and than comparisons pose additional problems when the noun following as or than is the subject or object of an implied clause. Does the sentence The employees are more suspicious of the arbitrator than the owner mean that the employees distrust the arbitrator more than they distrust the owner or that the employees distrust the arbitrator more than the owner does? To be clear you must add a verb to the second element of the comparison: The employees are more suspicious of the arbitrator than they are of the owner or The employees are more suspicious of the arbitrator than the owner is.
3
Of course, sentences containing as and than comparisons may be unambiguous but still be in need of balancing. Here are two other examples:
More than twice as many tons of corrugated cardboard are recycled each year than (are tons of) newspaper.
The factory is producing as many transmissions as (it did) last year.
4
The material in parentheses is often left out in sentences of this type, but parallelism requires it.
5
Making a syntactically imperfect comparison may not be the most grievous fault you can commit in writing, and nearly everyone makes these faults when speaking. But when you have the choice, why not be precise?
6
compound verbs
Jim knew that Candace had discovered the thief and felt it was OK to tell the reporters. Here we have verbs that are parallel but ambiguous. Who felt it was OK to tell the reporters, Jim or Candace? When the first part of a compound verb is followed by a subordinate clause, the second part of the verb may appear to belong to the subordinate clause. In these cases, it’s best to give the second verb its own subject: Jim knew that Candace had discovered the thief, and he felt it was OK to tell the reporters. As an alternative, you can recast the sentence to avoid the parallelism: Once Jim knew that Candace had discovered the thief, he felt it was OK to tell the reporters.
7
either … or / neither … nor
You should follow both conjunctions
in either … or … (or neither … nor …) constructions with parallel elements. If you follow either with a verb and an object, or must have a verb and an object as well. Thus you should say She can either take the examination offered to all applicants or ask for a personal interview but not She can take either
