"Life expectancy" is the average age at death of the entire live-born

Only B weakens the conclusion that 40 year olds in the nineteenth century were considered old.
It says that the average went up because deaths of 1 year olds decreased dramatically.
So the people who are considered old remains to be of the same age.
Does this help?
Which option do you think is better?

B talks about last 150 years which may include both nineteenth century and "Now". so how can we say that the data for infant deaths apply to only nineteenth century??

Nope. It says in the last 150 years. That phrase would not include what happened now.

Hope this helps.

hello experts,

I am unable to comprehend what the argument is trying to convey here. Below are my thoughts on this

Premise: - "Life expectancy" is the average age at death of the entire live-born population. In the middle of the nineteenth century, life expectancy in North America was 40 years, whereas now it is nearly 80 years.

Conclusion: - Thus, in those days, people must have been considered old at age that we now consider the prime of life.

- The question stem asks us to WEAKEN the argument i.e. we need to find an option that says people, in those days, at the age of 40 shouldn't have been considered old

- None of the options relate to what I am thinking here hence I am stuck. Request your help. Thanks

"Life expectancy" is the average age at death of the entire live-born population. In the middle of the nineteenth century, life expectancy in North America was 40 years, whereas now it is nearly 80 years. Thus, in those days, people must have been considered old at age that we now consider the prime of life.

Which of the following, if true, undermines the argument above?

(A) In the middle of the nineteenth century, the population of North America was significantly smaller than is today.
Irrelevant

(B) Most of the gains in life expectancy in the last 150 years have come from reductions in the number of infants who die in their first year of life.
Good

(C) Many of the people who live to an advanced age today do so only because of medical technology that was unknown in the nineteenth century.
Irrelevant

(D) the proportion of people who die in their seventies is significantly smaller today than is the proportion of people who die in their eighties.
Irrelevant

(E) More people in the middle of the nineteenth century engaged regularly in vigorous physical activity than do so today.
Irrelevant

What a shame that I missed this 25% difficulty one. Let’s sort it out:
Life expectancy is the average age at death of the entire live-born population. 19 century life expectancy was 40 years, however now it’s 80 years.
Conclusion: in 19 century people at 40 should be considered at old age. In order to undermine this conclusion I should show that those at their 40 were not considered old.
A. Tries to play a trick by introducing the number of the population.
C. Talks about current people instead of showing why people in 19 century were not considered old at their 40. This was my initial choice because I didn’t get the meaning of the choice B.
D. Irrelevant
E. Saying that vigorous action had some negative effect on life expectancy will be an unwarranted assumption.

B. First I didn’t understand the logic behind, but B says that relatively high infant death rate reduced the life expectancy of 19 century people. If that is true, most people then didn’t die around 40 but they could live up to 80 while most infants died within first year of birth.

AndrewN

Not able to get to the meaning of this question. Can you please help.

Hello, warrior1991. Pardon me for being so literal if my interpretation of your query is off, but I thought I would point out that this is a typical weaken-the-argument question, one that hinges upon one of the three "under"s: undercut (strongly go against), undermine (go against), and underscore (strengthen).



Here, our task is to weaken the argument, so we have to pay attention to what, exactly, that argument says. Luckily for us, this one is relatively straightforward, with a conclusion marker in thus and everything. The passage:



Our task is to weaken this notion that a 40-year-old in the middle of the nineteenth century must have been considered old. Since "life expectancy" is defined as the average age at death of the entire live-born population, we cannot consider still births, but we can consider babies who were born alive but may have died soon after. Looking at the answer choices, following a linear pathway to weaken the argument, we can see that just a single answer provides a rational explanation that would hamper the argument. (It must deal with lowering the number of years of life expectancy but allow for 40-year-olds not to be considered old.)


A smaller (or larger) population has no bearing on the life expectancy. The argument could still hold regardless.


Notice the hint in most. When you come across these sorts of qualifying words (superlatives), you should take note. They tend to either lead to an overreaching statement or go out of their way to qualify a reasonable answer. If life expectancy has risen because the number of infants who die in their first year of life has decreased in a significant way, then perhaps a 40-year-old of the time period in question would not have been considered so old after all, and the conclusion of the passage would, in fact, lose traction.


This new information provides an explanation as to why people today might live longer, but it does nothing to weaken the argument that people around the age of 40 during the middle of the nineteenth century would have been considered geriatrics.


Why are we concerned exclusively with people of today when the argument is based on people of the past? This is another easy elimination.


Good for them, but they could still have worn out their fit bodies by the time they were 40 or so, and people at the time could have still perceived them as old. This cannot be our answer.

I hope that helps. I had a lot of fun with this one, and, as always, I appreciate your calling my attention to another question.

- Andrew

GMATNinja But the AO B and C have the words most and many. So, shouldn't I already eliminate them since it doesn't cover the entire population?

VeritasKarishma mam please guide for this question.... I am able to eliminate other options by POE, however I am unable to understand why Option B is correct and what is the relevance for timeline 150 years here

vasuca10

"Life expectancy" is the average age at death of the entire live-born population.
So if population consisted of 10 people such that 4 died when they were 1 yr old, 2 died when they were 40 yrs old and 4 died when they were 79 years old, "Life expectancy" = 40.


In the middle of the nineteenth century, life expectancy in North America was 40 years, whereas now it is nearly 80 years.

In 1850 (middle of 19th century), LE = 40 yrs
Now in 2020, LE = 80 yrs

Conclusion:
Thus, in those days, people must have been considered old at age that we now consider the prime of life.

Conclusion says that in 1850, 40 must have been considered old age. What will weaken this?

(A) In the middle of the nineteenth century, the population of North America was significantly smaller than is today.

Actual population size is irrelevant.

(B) Most of the gains in life expectancy in the last 150 years have come from reductions in the number of infants who die in their first year of life.

In the last 150 years, deaths of infants has reduced. That is why LE has gone up (mostly).
So instead of 4 babies dying at 1 yr old, only 1 dies at that age now. Rest 3 die at 79. The LE goes up.
So this option tells us that LE was low not because everyone was dying sooner but because too many infants were dying. Mostly people may still have been living to the ripe old age of 60 - 70 if they survived the first few years. Hence old age then and now may be no different. The actual difference lies in the number of infants surviving now.

(C) Many of the people who live to an advanced age today do so only because of medical technology that was unknown in the nineteenth century.

This says that people live longer lives now due to advantaged tech. Doesn't weaken our conclusion.

(D) the proportion of people who die in their seventies is significantly smaller today than is the proportion of people who die in their eighties.

Doesn't tell us what happened in 1850.

(E) More people in the middle of the nineteenth century engaged regularly in vigorous physical activity than do so today.

Irrelevant.

Answer (B)

"Life expectancy" is the average age at death of the entire live-born population. In the middle of the nineteenth century, life expectancy in North America was 40 years, whereas now it is nearly 80 years. Thus, in those days, people must have been considered old at age that we now consider the prime of life.

Premise: life expectancy is now 80. in mid 19th century, it was 40
Conclusion: prime of life now is at the time people in the past considered old age. It means that now 30 is prime time. Back then, 30 is old already

Which of the following, if true, undermines the argument above?

To undermine this argument, a different reason should be presented to explain the gain in life expectancy at the moment other than people live longer now

(A) In the middle of the nineteenth century, the population of North America was significantly smaller than is today. Not relevant to the argument

(B) Most of the gains in life expectancy in the last 150 years have come from reductions in the number of infants who die in their first year of life. Oh yes. So we could not connect the gain in life expectancy with people living longer

(C) Many of the people who live to an advanced age today do so only because of medical technology that was unknown in the nineteenth century. So what. It doesn't address the conclusion

(D) the proportion of people who die in their seventies is significantly smaller today than is the proportion of people who die in their eighties. couldn't care less

(E) More people in the middle of the nineteenth century engaged regularly in vigorous physical activity than do so today. why on earth this option is here?

You shouldn't eliminate an answer choice purely because of one word in the answer -- take the time to examine what the answer choice means as a whole before eliminating it.

First, let's take a look at (C):

The word "Many" at the start of this answer choice does refer to a group of people in (C). However, that group of people is those "who live to an advanced age today." This is a different population to the entire population referred to in the passage. So, we need to do a bit more thinking before we can eliminate the answer choice.

The argument in the passage is contrasting the age at which someone would be considered "old" in the nineteenth-century to the age at which they would be considered "old" now. (C) gives us information about why the people who live to "an advanced age" now have done so.

Knowing why a person has lived to this advanced age doesn't help undermine the argument that the age at which a person is considered "old" has changed. For that reason, (C) can be ruled out as an answer to this question.

Now, let's examine (B):

The "Most" at the start of this answer doesn't refer to a group of people, it tells us about the gains in life expectancy. While this definitely doesn't refer to the whole population as in the passage, we should do a little more thinking before eliminating (B).

From the passage, we know that life expectancy is just the average age at death of everyone in the population. (B) tells us that most of the gains in life expectancy in the last 150 years have come from reducing the number of babies who die before they reach their first birthday.

By reducing the number of babies dying before their first birthday, these people will live longer and the average age of death of the population will rise. It's not that people in the population are living longer -- it's that the babies who were dying when they were very young and dragging the average down are now living longer. Therefore, it is not necessarily true that people would have been considered "old" at a younger age than the age they are considered "old" now.

When considered as a whole, (B) undermines the argument successfully and is the answer to this question.

Eliminating answer choices because one or two words don't match what was said in the passage can get very risky! Instead, thinking about the answer choice as a whole should help you understand why you're making each elimination in a question.

I hope that helps!

Average age was 40 - Low because lot of deaths at small age? Allegation approach from Quant
(B) Most of the gains in life expectancy in the last 150 years have come from reductions in the number of infants who die in their first year of life.

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