The population of Megacity, a sprawling metropolis .....

[prashant.ranjan]

The population of Megacity, a sprawling metropolis in Remsland, has grown at a fairly steady rate for over a century. A hundred years ago, poor sanitation in the city caused high mortality rates among the city's inhabitants, and what fueled the population increase was immigration from rural villages. This immigration has continued and even increased. Moreover, in recent decades, city sanitation has improved enormously. Yet the city's population growth has not significantly accelerated.

Which of the following, if true, most helps to explain why the city's population growth rate has not changed?
A. Mortality rates that were associated with poor sanitation in Megacity a hundred years ago were orders of
magnitude higher than are mortality rates associated with vehicular traffic, which is currently a major cause of
death in the city.
B. For several decades, Megacity, as distinct from the countryside, has had a steadily declining birth rate.
C. Cities smaller than Megacity have also experienced sustained population growth.
D. The great majority of immigrants to Remsland settle in Megacity, at least initially.
E. Megacity has long offered better employment prospects than most rural areas.

The above question is from GMAT Prep. I selected choice (A) as the answer while the OA is (B).
The reason for selecting (A) was, since vehicular traffic is the major cause of the death in the city, that explains why the population has not significantly increased.
While (B) says that Megacity had a steady declining birth rate. While I think steady declining birth rate explains why there was not a significant accleration in the population of Megacity.... why vehicular traffic cannot be the reason for the cause of no increase in the population.

------------
Just to confirm my line of thinking...I think i can understand why (A) can't be the answer.

Megacity's sanitation has improved ENORMOUSLY. So the Most Probable Interpretation of this fact would be that in Megacity the deaths are not happening because of sanitation. There must be some other cause why the population burst is not happening.

The reason may be because major cause of death rates only means that people decease mainly due to accidents and not because of sanitation issues. The no. of deaths caused by traffic accidents can still be low and at the same time be the major cause. It doesn't help to explain why there shouldn't be population increase. For e.g. the population of a country can still increase tremendously even if a lot of people die in train accidents (major cause of death).
While (B) surely guarantees that even if the sanitation has improved but if there is a steady decline in birth rate, the population will not significantly accelerate.

Kindly confirm if I am correct in my line of reasoning.

Thanks and Regards
Prashant
-----------
Big Fan :)

[jnelson0612]

Prashant,
I'm sorry; I read that a few times and I'm still not sure if I followed it. Let me try to lay this out as simply as possible:

In this type of question we are asked to explain the occurrence of an odd situation.

Let's look at the facts:
--In the past, sanitation in the city was terrible and killed a lot of people. At the same time, people continually immigrated in from the surrounding area. The population growth resulted from the immigrants coming in, and the population grew at a steady rate.

--Sanitation has improved a lot, so it is no longer killing people. People continue to immigrate in. We would expect there to be a population explosion . . . people aren't dying and people are arriving. However, the population growth has not increased. Why? We have to choose the answer that best explains this odd situation.

How to explain:
We have two groups of people: those already living in the city and those coming in. The coming in group has been steady all along. Fewer people from the current group are dying from disease. Shouldn't there be a lot more people? No, as long as the number of people born to the already there group decreases. As those people die out from natural causes they are not replaced with new babies. Thus, the growth rate stays the same.

Please let me know if I can clarify further. :-)

--As a result, we would expect

[jyothi h]

The population of Megacity, a sprawling metropolis in Remsland, has grown at a fairly steady rate for over a century. A hundred years ago, poor sanitation in the city caused high mortality rates among the city's inhabitants, and what fueled the population increase was immigration from rural villages. This immigration has continued and even increased. Moreover, in recent decades, city sanitation has improved enormously. Yet the city's population growth has not significantly accelerated.

Which of the following, if true, most helps to explain why the city's population growth rate has not changed?
A. Mortality rates that were associated with poor sanitation in Megacity a hundred years ago were orders of
magnitude higher than are mortality rates associated with vehicular traffic, which is currently a major cause of
death in the city.
B. For several decades, Megacity, as distinct from the countryside, has had a steadily declining birth rate.
C. Cities smaller than Megacity have also experienced sustained population growth.
D. The great majority of immigrants to Remsland settle in Megacity, at least initially.
E. Megacity has long offered better employment prospects than most rural areas.

The above question is from GMAT Prep. I selected choice (A) as the answer while the OA is (B).
The reason for selecting (A) was, since vehicular traffic is the major cause of the death in the city, that explains why the population has not significantly increased.
While (B) says that Megacity had a steady declining birth rate. While I think steady declining birth rate explains why there was not a significant accleration in the population of Megacity.... why vehicular traffic cannot be the reason for the cause of no increase in the population.

------------
Just to confirm my line of thinking...I think i can understand why (A) can't be the answer.

Megacity's sanitation has improved ENORMOUSLY. So the Most Probable Interpretation of this fact would be that in Megacity the deaths are not happening because of sanitation. There must be some other cause why the population burst is not happening.

The reason may be because major cause of death rates only means that people decease mainly due to accidents and not because of sanitation issues. The no. of deaths caused by traffic accidents can still be low and at the same time be the major cause. It doesn't help to explain why there shouldn't be population increase. For e.g. the population of a country can still increase tremendously even if a lot of people die in train accidents (major cause of death).
While (B) surely guarantees that even if the sanitation has improved but if there is a steady decline in birth rate, the population will not significantly accelerate.

Kindly confirm if I am correct in my line of reasoning.

Thanks and Regards
Prashant
-----------
Big Fan :)

As per my understanding ---

Option "A" doesnt fully answer our question about why the city's population growth has not changed ( increased).
All it says here is - hundred years ago deaths due to sanitation was greater than deaths due to traffic - and currently death due to traffic is greater than any other death cause ( sanitation).
hundred years ago - Sanitation death could be 30/month and traffic death rate could be 20/month. - totals to 50/month
currently - sanitation death could be 10/month and traffic death could be 20/month - totals up to 30/month .
So the total deaths per month is lesser now and there is still an influx of rural immigrants .All we know from passage is that the death due to sanitation has decreased.But total death due to traffic + sanitation could be greater than before or less. If you consider the above eg - the population growth should accelerate instead of decelerate. So in this case it tends to hurt the argument rather than support .
Hence this option doesnt really help answer our question.

[jlucero]

As per my understanding ---

Option "A" doesnt fully answer our question about why the city's population growth has not changed ( increased).
All it says here is - hundred years ago deaths due to sanitation was greater than deaths due to traffic - and currently death due to traffic is greater than any other death cause ( sanitation).
hundred years ago - Sanitation death could be 30/month and traffic death rate could be 20/month. - totals to 50/month
currently - sanitation death could be 10/month and traffic death could be 20/month - totals up to 30/month .
So the total deaths per month is lesser now and there is still an influx of rural immigrants .All we know from passage is that the death due to sanitation has decreased.But total death due to traffic + sanitation could be greater than before or less. If you consider the above eg - the population growth should accelerate instead of decelerate. So in this case it tends to hurt the argument rather than support .
Hence this option doesnt really help answer our question.

One small clarification on A- they are comparing the mortality rates of poor sanitation 100 years ago vs the mortality rates of vehicular traffic today. There's no grouping of these rates together back then or now:

Mortality rates [then] (that were associated with poor sanitation in Megacity a hundred years ago) were orders of
magnitude higher than are mortality rates [now] (associated with vehicular traffic, which is currently a major cause of
death in the city).

As you said, option A doesn't explain why the growth rate hasn't changed, but part of the reason is that it simply compares two unrelated mortality rates from two different eras.

[jyothi h]

As per my understanding ---

Option "A" doesnt fully answer our question about why the city's population growth has not changed ( increased).
All it says here is - hundred years ago deaths due to sanitation was greater than deaths due to traffic - and currently death due to traffic is greater than any other death cause ( sanitation).
hundred years ago - Sanitation death could be 30/month and traffic death rate could be 20/month. - totals to 50/month
currently - sanitation death could be 10/month and traffic death could be 20/month - totals up to 30/month .
So the total deaths per month is lesser now and there is still an influx of rural immigrants .All we know from passage is that the death due to sanitation has decreased.But total death due to traffic + sanitation could be greater than before or less. If you consider the above eg - the population growth should accelerate instead of decelerate. So in this case it tends to hurt the argument rather than support .
Hence this option doesnt really help answer our question.

One small clarification on A- they are comparing the mortality rates of poor sanitation 100 years ago vs the mortality rates of vehicular traffic today. There's no grouping of these rates together back then or now:

Mortality rates [then] (that were associated with poor sanitation in Megacity a hundred years ago) were orders of
magnitude higher than are mortality rates [now] (associated with vehicular traffic, which is currently a major cause of
death in the city).

As you said, option A doesn't explain why the growth rate hasn't changed, but part of the reason is that it simply compares two unrelated mortality rates from two different eras.

Thank you for the reply , Joe !

But , As per the statement A -
"A. Mortality rates that were associated with poor sanitation in Megacity a hundred years ago were orders of
magnitude higher than are mortality rates associated with vehicular traffic, which is currently a major cause of
death in the city."

I think, it meant,
----- the mortality rate due to poor sanitation was greater than Mort Rate due to vehicular traffic - hundreds of years ago.
------ But now , Mort Rate due to Vehicle is greater than that due to poor sanitation ( is wht they mean by - "which is currently a major cause of death").

So they are correctly comparing sanitation and vehicular mort rates of both eras . Just that this information does not help answer our question, as per my understanding in my previous post.

Not sure if I am interpreting it wrongly. If so, then request you to clarify the point I am missing.
Thanks !

[tim]

i think you've got the primary idea here, which is that A can't be the answer because it doesn't address what we need it to.. :)

[jyothi h]

i think you've got the primary idea here, which is that A can't be the answer because it doesn't address what we need it to.. :)

Ok ! :)

[tim]

:)

[mahendru1992]

Why not D. The option says that most immigrants settle in Remsland but only initially. Who's to say that they don't move on to some other place. This can be a major cause of population not increasing since most immigrants who settle actually don't stay but move on.

[jlucero]

Why not D. The option says that most immigrants settle in Remsland but only initially. Who's to say that they don't move on to some other place. This can be a major cause of population not increasing since most immigrants who settle actually don't stay but move on.

There's a lot of assumptions that you are making in order to make answer D work. But you could generally do that with any answer choice: the sky is blue, and who's to say that if the sky is blue, then the population growth won't skyrocket. No. The correct answer will be the one that will best explain the conclusion without needing extra assumptions.

[mahendru1992]

Why not D. The option says that most immigrants settle in Remsland but only initially. Who's to say that they don't move on to some other place. This can be a major cause of population not increasing since most immigrants who settle actually don't stay but move on.

There's a lot of assumptions that you are making in order to make answer D work. But you could generally do that with any answer choice: the sky is blue, and who's to say that if the sky is blue, then the population growth won't skyrocket. No. The correct answer will be the one that will best explain the conclusion without needing extra assumptions.

Hi, Thanks for answering my question. I get your point but the thing I don't understand is that I'm not making any assumptions, just inferences (IMO)
D says The great majority of immigrants to Remsland settle in Megacity, at least initially
Here the choice specifically says that they settle only initially which means that they move one after some time? I'm getting confused here.
Thanks in advance

[RonPurewal]

The argument explicitly says that immigration has consistently caused the city's population to increase (and, furthermore, that this immigration is increasing). So you're trying to interpret this sentence in a way that contradicts what's actually written in the passage.

[harika.apu]

i think you've got the primary idea here, which is that A can't be the answer because it doesn't address what we need it to..

Hello Tim ,
My reasoning for option A
100 years ago - population increase by immigrants (i) + normal population =>collectively affected by high mortality rates
now = population increase by immigrants (>=i) + normal population =>affected by less mortality rates
If at all A is true, then population growth now should be more than 100 years ago

Am i right ?

[RonPurewal]

you have the right answer, but there's too much noise around it.

• first, explain the passage to a 9-year-old:
In the old days, germs killed lots of people. Now, germs hardly kill anyone.
People are still moving here.
Nothing is killing them as much as germs once did.
But the population isn't growing any faster.

• now, SPECIFY what a correct answer needs to do:
A correct answer must work AGAINST population growth.

basically, there are only three possibilities in the whole universe:
1/ More people are leaving (the passage mentions only immigration, not emigration);
2/ Not as many people are being born;
3/ More people are dying for some NEW reason.

(it's not ALWAYS possible to come up with such exact specifications... but, IF YOU CAN, you always should!)


once you have this, you can take one glance at choice A and say 'hmm, that's something that works TOWARD population growth.'
i.e., you want 'black', and A is 'white'.
eliminate.
definitely no need to create 'equations' in your head!

[harika.apu]

you have the right answer, but there's too much noise around it.

• first, explain the passage to a 9-year-old:
In the old days, germs killed lots of people. Now, germs hardly kill anyone.
People are still moving here.
Nothing is killing them as much as germs once did.
But the population isn't growing any faster.

• now, SPECIFY what a correct answer needs to do:
A correct answer must work AGAINST population growth.

basically, there are only three possibilities in the whole universe:
1/ More people are leaving (the passage mentions only immigration, not emigration);
2/ Not as many people are being born;
3/ More people are dying for some NEW reason.

(it's not ALWAYS possible to come up with such exact specifications... but, IF YOU CAN, you always should!)


once you have this, you can take one glance at choice A and say 'hmm, that's something that works TOWARD population growth.'
i.e., you want 'black', and A is 'white'.
eliminate.
definitely no need to create 'equations' in your head!

Yes Ron . Totally Agree