I have just discovered the opinion of that huge book (1,700 pages +) A COMPREHENSIVE GRAMMAR OF THE ENGLISH LANGUAGE written by those four brilliant scholars: Quirk, Greenbaum, Leech, and Svartvik.
They give this sentence (on p. 715 in my 1985 edition):
“The price of oil is up again today.”
a. They do not label “up” an adverb.
b. They do not label “up” an adjective.
c. They do not label “up” a preposition.
They label “up” in that sentence a so-called prepositional adverb.
They illustrate the difference with these two sentences (p. 713):
A car drove past the door. = preposition.
A car drove past. = prepositional adverb.
Can we, therefore, say:
a. The turnover is up. = prepositional adverb.
b. The turnover is up ten percent. = preposition. (Can we say that “ten percent” is the complement of the preposition 'up"?)
(P.S. That would explain why Beeesneees told us that we should not add the word “by,” for the sentence already has a preposition, i.e., “up.”)
How do we parse “is” in that sentence? Is it a full verb or only a linking verb?
a. On page 684, they give these examples:
i. The horses jumped over the fence.
ii. The horses are over the fence.
The four scholars say that “are” in that sentence indicates “the state of having reached the destination.” That is, The horses “have now jumped over.” They seem to be saying that that “are” is much more than a linking verb.
Thank you, James. I also have this book by Randolph Quirk and others. I’m happy that they have said it is a prepositional adverb, and not an adverbial preposition. Let’s close this chapter now.
I believe that “past” in the first sentence is analyzed as a preposition.
Here is a dictionary example: We went past the house by mistake.
If you did not have a complement (“the house”), then it would be a so-called prepositional adverb: We went past by mistake.
Those four scholars said that if you stress (say the word strongly), it is a prepositional adverb; if you do not stress it, then the word is a preposition.
My bad examples:
The elevator was out of order. So I walked UP. (prepositional adverb because you stress “up”)
The elevator was out of order. So I walked up THE STAIRS. (preposition because in speech you do not stress “up”)
M-W give one definition of adjectival “up” as “being above a former or normal level (as of quantity or intensity)”, and give the example “attendance is up”, which to me seems incredibly similar to “The turnover is up”.