Forecast

[goelmohit2002]

source GMATPrep

To develop more accurate population forecasts, demographers have to know a great deal more than now about the social and economic determinants of fertility.

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
C. would have to know a great deal more than they do now about the social and economical
D. would have to know a great deal more than they do now about the social and economic
E. would have to know a great deal more than now about the social and economic

OA = D...can someone please tell what is wrong with A and E ?

[mikrodj]

in A and E you are not comparing similar things

demographers have to know a great deal more than now about social and economic ...

literally you're comparing the knowledge about social and economic determinants to now.

Consider the following example

I have to run faster than now.

This is clear incorrect. what is now? This doesn't make any sense

I have to run faster than I do now. Correct

[goelmohit2002]

Thanks mikrodj

[RonPurewal]

don't forget the difference between "economic" and "economical", which is huge.
"economic" means "having to do with "economics and/or the economy". (this is the intended meaning.)
"economical" means "efficient" or "at low cost/expense". (this is not the intended meaning.)

i think this sentence makes sense with either "would have to" or "have to". there's a slight rhetorical difference ("would have to" carries the connotation that these forecasts are just hypothetical and don't actually have to be developed, or that at least it's not important, while "have to" implies that these forecasts are important and have to be made), but you don't have to make such rhetorical distinctions on the exam.
in this case, you don't have to, since both choices involving "have to" (without "would") are wrong for other reasons.

(a) is only wrong for the reason mentioned by the poster above me.

[acethegmat]

Sorry Ron, if this question sounds silly, but if there is an AC with the option - 'will have to', wouldn't that be a better choice than 'would have to' ?

Thank you.

[mschwrtz]

Not a silly question at all. The answer is no, that would not be better. Neither would it be worse. So they won't give you both options in otherwise-correct sentences.

There is a very slight difference in meaning between "would" and "will" in this context, but it's much too subtle a difference to matter on the GMAT.

[deepakdewani]

Hi Ron,

In one of the other threads that I have seen (and I am sure that in several others), you mentioned that in parallel constructions, if the verb in the second part of the construction is "absolutely the same" as in the first part of the construction, then that verb may be omitted in the secod part.

My question is: Can't the above principle be applied to Choice A above since the omitted portion in the second part, i.e. "they know" has the exaclty same verb as the first part?

Thank you for your help.

[RonPurewal]

Hi Ron,

In one of the other threads that I have seen (and I am sure that in several others), you mentioned that in parallel constructions, if the verb in the second part of the construction is "absolutely the same" as in the first part of the construction, then that verb may be omitted in the secod part.

My question is: Can't the above principle be applied to Choice A above since the omitted portion in the second part, i.e. "they know" has the exaclty same verb as the first part?

Thank you for your help.

yep, i did say that. unfortunately, that principle does not apply here, since the verb that you're trying to omit is not exactly the same as its counterpart.
specifically, the first verb is in a hypothetical/conditional tense (would have to know...), while the second verb is in the present tense (they do [= know] now). you are not allowed to imply such tense transitions.
if you omit the verb, the omitted verb will be assumed to be in the same tense as its parallel counterpart. since you have to change tenses in this problem, you must include both verbs.

[prepgmat09]

Hi Ron,

Regarding the elliptical construction question above, can we not think of "they know" as omitted in the original choice. In that case, A would read:

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.

Would this choice be incorrect? If yes, could you please explain, why? How should the reader comprehend that this sentence was meant to be written in hypothetical form and so the ommission of words in the second part of comparison does not work here.

Thanks.

[mschwrtz]

First, they know isn't a verb, it's a clause.

Second.... No, as Ron pointed out in the immediately prior post, the first verb has a tense marker, would have, which the ellipsed verb could not share. So there's no ellipsed verb.

Even absent this tense marker, I wouldn't read an ellipsis here.
To a certain extent, this is an empirical question. You wouldn't get perfect consensus from a panel of grammar experts on the circumstances under which we should infer ellipsis, so the relevant empirical question is, Under what circumstances does the GMAT allow verbs to be ellipsed in parallel structures?

In every GMAT SC case that I can think of where such ellipsis is permitted, the ellipsed verb is unambiguously necessary from the moment the reader gets to the ellipsis. That is not the case here, because they must know more than could be followed by a clause or a noun.

However, since this is an empirical claim, I welcome counter-examples from the GMAT.

[nipunkathuria]

Hi Ron,

as far as i know, "would" is always used in a construct where we are dealing with "past tense".
When i was working out this problem, i just eliminated the options "would"
Can u plz shed some light on this..

[RonPurewal]

Hi Ron,

as far as i know, "would" is always used in a construct where we are dealing with "past tense".
When i was working out this problem, i just eliminated the options "would"
Can u plz shed some light on this..

"WOULD" AND "COULD"
These words have 2 different incarnations.

Usage #1
"Would" is the past tense of "will", and "could" is the past tense of "can".
e.g.
According to his most recent advertisement, Mookie the Bookie can predict with 100% accuracy which teams will win next week’s games.
vis-à-vis
His October 2, 1982, advertisement declared that Mookie the Bookie could predict with 100% accuracy which teams would win the following week’s games.

Usage #2
"Would" and "could" are used to describe hypothetical situations that are not true, or are extremely unlikely. (since these situations are hypothetical -- i.e., they never happened -- they don't really have a timeframe.)
e.g.
If I had one million dollars, I could buy 800,000 hamburgers at the gas station.
If I had one million dollars, I would donate 800,000 hamburgers to the county food bank.

--

in this problem "would" is the second type.

[rx_11]

Hi Ron,

In one of the other threads that I have seen (and I am sure that in several others), you mentioned that in parallel constructions, if the verb in the second part of the construction is "absolutely the same" as in the first part of the construction, then that verb may be omitted in the secod part.

My question is: Can't the above principle be applied to Choice A above since the omitted portion in the second part, i.e. "they know" has the exaclty same verb as the first part?

Thank you for your help.

yep, i did say that. unfortunately, that principle does not apply here, since the verb that you're trying to omit is not exactly the same as its counterpart.
specifically, the first verb is in a hypothetical/conditional tense (would have to know...), while the second verb is in the present tense (they do [= know] now). you are not allowed to imply such tense transitions.
if you omit the verb, the omitted verb will be assumed to be in the same tense as its parallel counterpart. since you have to change tenses in this problem, you must include both verbs.

Hi, Ron

I got a sentense on the MGMAT SC 4th page 129.

Right--- I walked as fast now as (I walked) when I was younger.

The part that is in the "()" is omitted. Why is this sentense still correct according to your explanations? Because you said " if you omit the verb, the omitted verb will be assumed to be in the same tense as its parallel counterpart." This sentense seems not to apply to this rule. Can you clarify that?

[RonPurewal]

I got a sentense on the MGMAT SC 4th page 129.

Right--- I walked as fast now as (I walked) when I was younger.

The part that is in the "()" is omitted. Why is this sentense still correct according to your explanations? Because you said " if you omit the verb, the omitted verb will be assumed to be in the same tense as its parallel counterpart." This sentense seems not to apply to this rule. Can you clarify that?

will have to look at that.

this is one of those cases in which it's the official precedent(s) that matter the most; the rule i've propounded above comes from what i've seen in the official problems.
if i can find official precedents to the contrary, then i'll post corrections. thanks.

[rx_11]

I got a sentense on the MGMAT SC 4th page 129.

Right--- I walked as fast now as (I walked) when I was younger.

The part that is in the "()" is omitted. Why is this sentense still correct according to your explanations? Because you said " if you omit the verb, the omitted verb will be assumed to be in the same tense as its parallel counterpart." This sentense seems not to apply to this rule. Can you clarify that?

will have to look at that.

this is one of those cases in which it's the official precedent(s) that matter the most; the rule i've propounded above comes from what i've seen in the official problems.
if i can find official precedents to the contrary, then i'll post corrections. thanks.

Dear Ron,

I think I've found an example of the official problems. However, it is an OG question, and I know you can't answer OG questions because of the copyright problem.(OG12th 93).

So I have just somewhat changed the sentense. Hope it would avoid the copyright problem.

"The products prices are higher this year than (the prices were) last".

The part that is in the "()" is omitted. Could you explain why we can still omit "the prices were" despite that the two clause's tenses are different?