Hi,

I think Ron is doing a great job trying to help you understand every rule in play on the GMAT. That said, you need to learn to use a general framework to aid you in tough situations such as this one. In this case just ask yourself whether there is ambiguity caused by omitting "the prices were."



First off, let's check on what's being compared - times when the prices were different. There are several ways this sentence can be written:

A. The product's prices are higher this year than the product's prices were last year
B. The product's prices are higher this year than the prices were last year
C. The product's prices are higher this year than they were last year
D. The product's prices are higher this year than last year
E. The product's prices are higher this year than last

In each of the versions, there is no ambiguity as to what is being compared. A and B, however, are awkward because of how wordy they are. In C at least, the pronoun they is used to make the sentence more concise with no change in meaning from A and B.

With D, the omission of "they were" doesn't degrade the meaning of the sentence. Why is that the case? Well, when you examine the sentence and focus on the comparison signal "higher X than Y" you notice that we're comparing when the prices were different. In this case, there isn't anything in the sentence to confuse this comparison in D, so it is completely fine to omit "they were"

On a final note, examine the omission of "year" at the end of E. It's pretty clear that "last" could only modify year so omitting year doesn't result in a loss of meaning. Still I strongly prefer D :)
Thanks,
Chris

_________________
Chris Brusznicki
MGMAT Instructor
Chicago, IL

Hi ron !
I also really confused about it, since in your prior post you said both "have to" and "would have to" make sense. so could you reply the post and make it clear?
thanks in advance.

hi,
please don't just mention "your prior post". i have almost 10,000 posts on this forum, so that's not particularly helpful.
i.e., please QUOTE any "prior post" to which you might refer. thanks.

--

either "have to..." or "would have to..." (or "will have to...", which doesn't appear in the choices) could work here.

"have to ..."
--> no implication about whether this is likely; just a matter-of-fact statement about what they need.
"would have to..."
--> implies that this is an unlikely (or even impossible) scenario.
"will have to..."
--> implies that this will be at issue sometime in the future. doesn't imply anything about whether demographers will be able to achieve this kind of knowledge, but says that they'll need it (and so will fail in their efforts if they don't succeed in obtaining the knowledge).

if you change "economical" to "economic" in choice (b), you would have another viable option.

_________________
Being well-dressed gives a feeling of inward tranquillity [that] religion is powerless to bestow.
C.F. Forbes

first of all, thanks for ron's great explanation again! but i will say sorry for you ron. in my post, because i didn't make my question clearly. i will promise next time i will examine what i say before i post! ACTUALLY MY QUESTION IS what prepgmat09 mention above "can we not think of "they know" as omitted in the original choice."
that is
To develop more accurate population forecasts, demographers have to know a great deal more than (they know) now about the social and economic determinants of fertility.

i will wait for your next great explanation! thanks

that doesn't work, because “they know” isn't in the first part. if a construction can be omitted, then the same construction should exist elsewhere in the sentence. here, it doesn't; the omitted portion would be assumed to correspond to “demographers have to know”, which doesn't make any sense.

_________________
Being well-dressed gives a feeling of inward tranquillity [that] religion is powerless to bestow.
C.F. Forbes

Hi Ron and Chris

I am getting even more confued with this, Ron mentioned that the verb-tense has to be the same in order to be omitted; however, the examples Chris gives hee, in D, E, they omitted part should be past tense while the other part is present tense...Could either of you please help to explain?

Thank you.

Some after thought, maybe Ron's explanation should apply to "Subject + Verb", and Chris's explanation shoud apply to "Subject + Be"?

well, the saving grace on that problem is that there are no choices that do have the second verb.
in other words, there aren't actually any choices that say "...to be higher this year than they were last year", so this becomes a non-issue.

if you see a SPLIT in which one choice looks like this and another choice actually has the two different verb tenses, then you should pick the choice with the two different verb tenses.

_________________
Being well-dressed gives a feeling of inward tranquillity [that] religion is powerless to bestow.
C.F. Forbes

Ron, experts, members, please comment.

In this problem, I think "than now" in A is correct because there is no ambuguity here. But, GMAT PREFERS TO USE "do" IN THE SECOND HALF OF THE COMPARISON EVEN WHEN THERE IS NO AMBUGUITY.This is the point. for example

I sing better than you do

is prefered to

I sing better than you.

this preference appears many times on gmatprep questions. That is why A and E are wrong.

I want you to confirm my thinking.

Moreover, gmat SC now focuses on meaning and logic, not on gmat rules such as this preference which requires remembering.

your analogy is not applicable here. in the example you gave, either form is correct, because we can compare "I" to "you" or "I sing" to "you do". can you provide any problem numbers from actual GMAT questions where this is an issue upon which the final answer relies? if not, i would recommend NOT internalizing any "rule" about a preference for one or the other of these..

in the GMAT Prep problem, the comparison is between (something) and "now", but there is no (something) that can properly be compared to "now"..

_________________
Tim Sanders
Manhattan GMAT Instructor

does the blue part in above quote means that correct sentence in original question of this thread implies - It is extremely unlikely that demographers require more data than they do know now

if not, please help me understand meaning of correct sentence

your use of the word "require", which does not show up in the correct sentence, is not appropriate here. in this case, "would" is used to indicate that demographers do not currently know enough to develop more accurate forecasts and that a situation where they do know enough is not imminent..

_________________
Tim Sanders
Manhattan GMAT Instructor

sorry to post link from another forum but statement above seems to directly contradict the statement made by ron at http://www.beatthegmat.com/demographers ... tml#399525 i think following 2 are equivalent and correct
a) have to know a great deal more than they do now about the social and economic
b) have to know a great deal more than they know now about the social and economic

Hi Vikram,
I'm not sure if you are making up these answers or if you are incorrectly transcribing answer choices A and B from the original problem. I put the originals down below just in case.

Otherwise, I would agree that those two answer choices you mentioned above are equivalent.

The actual answers are:
A. have to know a great deal more than now about the social and economic
B. have to know a great deal more than they do now about the social and economical

_________________
Jamie Nelson
ManhattanGMAT Instructor

sorry in case my last post confused you. actually my question is that in the link in my last post (above), ron says that have to know a great deal more than they do now about the social and economic is incorrect but, in his quote mentioned in my last post, he said that we can use this construction

this seems contradictory. may be it was just a typo in post in the link as i think we can use this construction

please clarify

i think the main point that you're missing here is what Ron said on August 30, 2009: "you don't have to make such rhetorical distinctions on the exam". unless the GMAT tests this, what does it matter if you've found what you think is a contradiction? Ron could say "the sky is green" and "the sky is red" and it wouldn't matter in the slightest if the GMAT is not in the habit of asking what color the sky is. please pay more attention to studying what is important rather than trying to pick apart irrelevant minutiae of Ron's posts..

_________________
Tim Sanders
Manhattan GMAT Instructor