The population of Megacity, a sprawling metropolis in Remsland, has gr

Question

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.

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AmoyV · Answer

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.  100 yrs ago Poor sanitation mortality higher than vehicular traffic mortality. Today poor sanitation mortality LOWER than vehicular traffic mortality. Doesnt explain the discrepancy. If 100 yrs ago vehicular traffic mortality rate was higher than poor sanitation mortality rate, then we wouldve had a winner here. 
B. For several decades, Megacity, as distinct from the countryside, has had a steadily declining birth rate.  Bingo. Population growth happens because of high birth rate coupled with low mortality. If mortality is now lower (assuming), then to have an insignificantly accelerating population, we need to have a declining growth rate (since we already know that immigration makes addition to the population of the city) 
C. Cities smaller than Megacity have also experienced sustained population growth.  OFS 
D. The great majority of immigrants to Remsland settle in Megacity, at least initially.  Goes against our discrepancy. This looks at making additions to the population. We need to know why the growth rate has not accelerated significantly. Also we don't know the time frame of "initially". So we don't know when they leave Megacity, if they do. 
E. Megacity has long offered better employment prospects than most rural areas.  OFS. Also it goes against the discrepancy. This fact would increase the population an hence would contribute to increasing the population growth rate. It tells us nothing about why the growth rate hasnt accelerated significanly

bhatiagp · Answer

Its B. The reason is that none of the other choices are strong enough to justify the stable growth rate despite increasing influx of immigrants. A is not strong enough, as the percentage is not mentioned.

prasannar · Answer

B for me.

The steady declining birth rate and increasing immigrant rate seem to be keeping a balance thus there is no significant growth in the city population.

fozzzy · Answer

Can someone explain option A. Is it incorrect since we have to resolve the paradox of why the population growth isn't high enough

whereas option A only provides an alternative reason for mortality rates?

Zarrolou · Answer

Before we had poor sanitary conditions and high emigration; now we have high sanitary conditions and high immigrations, but still the growth rate is stable.

A is incorrect because it provides us ( at best ) a weaker cause of death that replaced the poor sanitary conditions.

So now according to A we have 
A weaker cause of death than before and still high immigration. So the population should increase? 
The paradox is not solved.

JarvisR · Answer

P1:The population of Megacity, a sprawling metropolis in Remsland, has grown at a fairly steady rate for over a century. 
P2:A hundred years ago, poor sanitation in the city caused high mortality rates among the city's inhabitants.

P3: What fueled the population increase was immigration from rural villages. This immigration has continued and even increased.
P4:Moreover, in recent decades, city sanitation has improved enormously.

P5: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?

Q:why the city's population growth rate has not changed?
A: Its a pradox. Initially, declining population was stablized by immigration from rural villages , and then sanitory condition also got improved.
Ideally these favorable factors shall increase the population spordically but unfortunately that's not happening.

So what could go wrong?
What if there is another factor that is pulling down or cancelling the effect of improved sanitory conditions.In that case, the growth wont be as expected.

Now lets look at the given answer choices.

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.
>>Since we don't have any info about the mentioned magnitude, its difficult to gauge the impact.

B. For several decades, Megacity, as distinct from the countryside, has had a steadily declining birth rate.
>>Good. So if birth rates are declining then this factor can bring down the advantage of improved sanitary condition and would impact overall population growth.

C. Cities smaller than Megacity have also experienced sustained population growth.
>>Sounds neutral to me. Doesn't provide much info why the population is not increasing as it was expected.

D. The great majority of immigrants to Remsland settle in Megacity, at least initially.
>> Doesn't say what the trend now.So doesn't help much.

E. Megacity has long offered better employment prospects than most rural areas. 
>>Could be one of the reason why people migrate to city but doesnt explain why population is not growing as expected.

aceGMAT21 · Answer

I would like to add the excellent explanation by Ron, for this question,

• 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'.

rashedBhai · Answer

• 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!)

For several decades, Megacity has had a steadily declining birth rate. 
This answer choice explains why -- despite an increase in immigration from rural villages -- the population growth rate has not changed: FEWER BABIES are being born.

The correct answer is B.

zeniamehta · Answer

Issue:Population growth not increasing 
A- does not explain why population isn’t increasing 
B- directly attacks population growth 
C-out of context 
D-does nothing to explain the situation today 
E- this intact casts more doubt as to why people are still not moving to this city
Correct answer is B
E-

Posted from my mobile device

krittapat · Answer

GMATNinja   egmat   KarishmaB 
Could you please explain why option A is wrong?
Thanks for your help.

GMATNinja · Answer

This passage presents a something that seems like a contradiction.

To begin with, we're given two reasons why the population growth rate of Megacity should increase. First, immigration has "continued and even increased" over the past century. Second, "sanitation has improved enormously," which should decrease the mortality rate. Yet despite all of that, the city's population growth rate has not "significantly accelerated."

In other words: despite factors that should increase the population growth rate, this rate hasn't changed.

The question then asks  why  the city's population growth rate has not changed. So the correct answer should explain why this rate has not changed  despite  "continued and even increased" immigration and improved sanitation.

Let's now take a look at (A):

Based on the trends described in the passage, we'd expect the growth rate to increase, yet it hasn't actually increased. The correct answer should explain this contradiction. Does (A) do that?

Not really. According to (A), mortality rates from vehicular traffic are much less than the mortality rates from poor sanitation a century ago. If anything, this should cause the population growth rate to increase. In other words, (A) gives yet another reason why the population growth rate should  increase , so this wouldn't explain why the city's population growth rate  hasn't changed .

To explain that, we'd probably want some reason why the city's growth should decrease, thus cancelling out the effects of immigration and improved sanitation. Since (A) doesn't do that, it's wrong.

I hope that helps!

egmat · Answer

I can see why this question might be tricky – you've got two factors that should speed up population growth, but somehow the growth rate stays the same. Let me walk you through how to crack this paradox.

Here's what's happening:

The passage sets up a puzzle for us. Let's break down the key facts:

100 years ago:  High deaths from poor sanitation, but immigration from villages drove steady population growth 
  Today:  Immigration has  increased even more  + Sanitation has  improved enormously  (fewer deaths) 
  The puzzle:  Despite both improvements, population growth rate hasn't accelerated – it's stayed the same

Let's think about this logically:

Population growth depends on:  Births + Immigration - Deaths

The passage tells us:
 
 Immigration went UP ✓ 
 Deaths (from sanitation) went DOWN ✓

Both of these should make population grow faster! But it didn't. So there must be some  other factor  that's working in the opposite direction to offset these improvements.

Now let's evaluate the key choices:

Choice A:  This compares past sanitation deaths to current traffic deaths, but doesn't explain our puzzle. Even if traffic deaths are lower than old sanitation deaths, we still have more immigration AND fewer sanitation deaths – growth should still accelerate. This doesn't give us the offsetting factor we need.

Choice B:   This is our answer!  If birth rates in Megacity have been steadily declining for several decades, this gives us the missing piece. Think about it:
 
 Positive factors: More immigration + Fewer deaths from sanitation 
 Negative factor: Fewer births

The declining birth rate offsets the positive factors, keeping the overall growth rate steady. This perfectly explains why the growth rate hasn't changed!

Choice D:  Notice how this actually makes the paradox  worse ! If most immigrants to the entire country settle in Megacity, that's even MORE immigration pressure, which should make growth accelerate even more. This deepens the mystery rather than solving it.

Choice E:  Better employment prospects would attract more immigration, which again strengthens the paradox rather than resolving it.

The key insight:  For paradox questions, you need to find the missing factor that balances the equation. We had two factors pushing growth up, so we needed something pushing it down – and declining birth rates is exactly that offsetting factor.

Answer: B

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The population of Megacity, a sprawling metropolis in Remsland, has gr

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The population of Megacity, a sprawling metropolis in Remsland, has gr

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