Q21 - Thirty years ago, the percentage

[nanagyanewa]

hello,
Can someone please explain to me why answer choice C is right? I just can't understand how the kinds and quantities of food can justify the conclusion which is concerned with the rates of increases in prices. I chose answer D because I just put in random figures and realized that the prices of non-food items could rise faster than food items.

Thanks for your help in advance!

[ManhattanPrepLSAT1]

Good question!

We know that 30 years ago the percentage of income that single persons spent on food was twice what it is today. We also know that incomes have risen over the past 30 years.

The argument concludes that incomes have risen at a greater rate than the price of food.

This argument is vulnerable to a sharp criticism: namely, that the percentage of income spent on food could have dropped as a result of other changes in food consumption, not necessarily a change in the actual cost of food.

The key to seeing this one clearly is that the argument presents an observed phenomenon and concludes an explanation for why it happened. To strengthen an argument that takes this shape, you want to eliminate an alternative explanation. The one most obvious is that the drop in percentage is the result of changes in consumption rather than a change in price of food.

Answer choice (C) strengthens the argument by protecting the argument from the alternative explanation that the consumption patterns had changed, thus resulting in the drop in the percentage of income individuals spend on food.

(A) is tempting but we're not so concerned with the amount of food being consistent but the sorts of items being purchased being consistent.
(B) undermines the argument by providing an alternative explanation.
(D) is irrelevant. The price of nonfood items does not tell us whether food items increased in price or whether the drop in percentage was the result of some other factor.
(E) undermines the argument. Because if the resulting change for singles was the result of a change in food prices, that should have affected families as well.

Does this help clear this one up?

[hychu3]

But can't you say (A) strengthens the argument by protecting it against the alternative explanation that people simply eat more today and that is why they are spending greater portion of their income on food?

I believe we have an example of strengthen question where you're actually given two answer choices that strengthen the argument, and you're supposed to choose the stronger of the two.

In addition to doing what (A) is doing, (C) also protects the argument from the alternate explanation that people today eat kinds of food that are more expensive. That's why it is stronger.

Another point I want to make is that (C) says single persons today eat the same kinds of food in the same quantity as they DID 30 years ago.

It sounds like we're only talking about people who were alive 30 years ago instead of the whole population. In that case, (C) becomes a significantly weaker strengthener, and it can be argued that (A) is not necessarily the worse answer choice.

[ManhattanPrepLSAT1]

I like your attention to language hychu3!

Of course, I hope you then also see why I like the language in answer choice (C) as well. In answer choice (A) it discusses the amount of food eaten per capita. But in answer choice (C) it discusses the food eaten by single persons. What do they mean by single persons? Is the argument about all people or about single persons?

The stimulus refers to single persons, and I'm tempted to think that they mean people not in relationships. That makes me feel much more comfortable about the information in (C) being relevant to the argument whereas answer choice (A) being broader in scope. Additionally, the word DID in answer choice (C) does not make me think that they are only discussing those who were alive for the past 30 years, but rather single persons alive 30 years ago and single persons alive today.

(A) is tempting, but is not necessarily discussing the same group of people as was discussed in the stimulus, making me more comfortable with the relevance with the information in answer choice (C).

Hope that helps!

[Mab6q]

I felt like this argument has numerous flaws.

Conclusion: incomes have risen at a greater rate than the price of food.

WHY:

Percentage of income that single persons spent on food is twice as less as what it was 30 years ago.

and

Incomes have risen over the past thirty years.

Gaps in the reasoning:

1. The author assumes that we can make a broad claim about incomes and price of food a particular sample group: single persons.

2. Although we know that they spent twice as much 50 years ago, we don't know that they are buying the same amount

3. Just because incomes have risen in general, it doesn't mean incomes rose for single persons.

Answer choices:

The answer choices seemed to play at the second issue.

A. Is very tempting, but knowing the amount of food eaten tells us nothing about the amount of food purchased. I feel that is an important distinction that we have to be diligent about.

B. Weakens by suggesting that they are eating less.

C. does not prove the argument, but it helps. Tells us single persons purchased the same foods in same quantities . Hits at issue 2

D. non-food items are out of scope.

E. gets at our first issue, but weakens the argument. What is true of single persons is not true of others.

C is our answer.

[keonheecho]

I'm still a little confused on this...

The stimulus seems to also make the flawed assumption that because things were a certain way for single persons, that it would also be the same for people in general. Based off the evidence that single persons spent twice the percentage of income thirty years ago, they conclude that incomes have risen at a greater rate than the price of food for everyone. It seems to me that (A) bridges that gap somewhat. On the other hand, (C) only adds to the single person perspective, without showing how the data reflects people in general...
Also, someone mentioned that (A) is incorrect because the amount of food eaten is not the same as the amount bought, but wouldn't it still be a good indicator? I mean, you do have to buy food in order to eat it...I know the LSAT tends to avoid assumptions, but I've heard numerous times that common-sense assumptions are ok to make. Can someone further clarify why (A) is incorrect?

[WaltGrace1983]

I'm still a little confused on this...

The stimulus seems to also make the flawed assumption that because things were a certain way for single persons, that it would also be the same for people in general. Based off the evidence that single persons spent twice the percentage of income thirty years ago, they conclude that incomes have risen at a greater rate than the price of food for everyone. It seems to me that (A) bridges that gap somewhat. On the other hand, (C) only adds to the single person perspective, without showing how the data reflects people in general...
Also, someone mentioned that (A) is incorrect because the amount of food eaten is not the same as the amount bought, but wouldn't it still be a good indicator? I mean, you do have to buy food in order to eat it...I know the LSAT tends to avoid assumptions, but I've heard numerous times that common-sense assumptions are ok to make. Can someone further clarify why (A) is incorrect?

I'm going to go against the grain a bit and say that (A) and (C) are both good answers but (C) is significantly better.

People spent 2x the % on food 30 years ago as today
+
Incomes have risen over 30 years
-->
Incomes have risen at a greater rate than price of food

Assumption: the % statistic from 30 years ago is relevant to the % statistic today. In other words, people are generally buying the same food / same amount as before.

(B) "eating healthier" doesn't tell us much about quantity / type of food eaten. Plus, eating "less" than 30 years ago would actually weaken the argument because it shows that comparing the statistic between 30 years ago and today is actually less relevant.

(D) Don't care about "nonfood" items, just food items.

(E) This basically just validates the premise again. Premise booster.

(A) and (C) are pretty similar. I personally don't believe the "single persons" thing is too terribly significant, as you point out, because the conclusion is about incomes in general. I think "single persons" refers simply to each individual person, per capita.

(A) Amount of food eaten today = amount of food eaten 30 years ago

This looks good because it shows how the statistics can actually be compared.

(C) Amount of food purchased today = amount of food purchased 30 years ago AND type of food purchased today = type of food purchased 30 years ago.

This looks good because it shows how the statistics can actually be compared. However, it shows two things that are similar (amount AND type) rather than just one (like A). Also, it does refer to what is being purchased rather than eaten. This is a small distinction and I don't think it makes or breaks an answer BUT it does make (C) look even better.

Basically, (A) and (C) are similar but (C) unquestionably strengthens more, regardless of if (A) strengthens or not (I think it does slightly).

[todayztheday]

Some here have said non-food items are out of scope. Why? We have but 2 items in this economy: food, and non-food. This is a percentage question. 100% of single person's Income goes to one or the other of these 2 items. (D) says non-food has gone up in percentage. Thus, the only other item in the economy - food - must have gone down in %.

How can non-food be out of scope?

Further, that (C) single person buy the same food in the same quantities doesn't tell us about the price, does it? People can consume the same quantity and amount of Florida oranges but every hurricane season the cost of that consumption as a percent of income will increase(incomes otherwise fixed). (C) just says that when I make more, I don't consume more or different. It doesn't tell us about rate of price appreciation. What must be assumed for (C) to the right answer?

[williamkazenas]

I eliminated E immediately after I read "unlike single persons" because I saw that as out of scope.

Who cares what families do? The stimulus doesn't mention what families did in the past so I found this answer choice to be completely useless in confirming the argument.

Is this fair? Or would ya'll have considered this answer choice further seeing as it may have still been relevant to the conclusion in a more general way?

[haeeunjee]

OKAY. After hours of mulling, I think I now have it figured out.

We need to know two things in order for the conclusion to follow: (1) that the AMOUNT of food and (2) the TYPE of food is the same. Why? I'll go through my reasoning as succinctly as possible.

(1) AMOUNT: Like many people have said before, if I eat less now than I did 30 years ago, I am buying a smaller amount of food. This accounts for why the percentage of income spent on food is smaller. Thus, the conclusion that the price of food rose at a slower rate than the increase in income is challenged. Ex: Bananas cost 500% more ($1 to $6), but because I am buying so much fewer bananas, I'm actually spending less $ each year on bananas. My income did not rise 500% or more (that would be awesome wouldn't it??).

This is why (b) is wrong. People are eating less.

(2) TYPE: This is the tricky part. I only got this after eating my own dinner and thinking about it in very concrete terms. Let's say I love eating salmon steak. And every year, I eat a total of 50 lbs of it. In 30 years, the price of a single salmon steak has risen 300% (from let's say $15 to $60, not sure if math is correct, bear with me). I can't afford to buy a salmon steak for $60, especially if I eat 50 lbs of it every year! SO, I will change my eating preferences, and choose a different TYPE of fish, a cheaper version: canned tuna. Canned tuna also rose 300%, but it only went from $3 to $12. That I can definitely afford. And I can eat 50 lbs of canned tuna each year (blegh). Now, I can definitely afford my fish and if I completely switch from salmon steaks to canned tuna, I'm actually spending LESS each year on fish (salmon steak's old price of $15, canned tuna's new price of $12). The price of each individual food has risen ridiculously at a rate of 300%, yes, but I am able to spend less of my income on food because I have switched over to a cheaper alternative.

This is why (a) is wrong. I have not changed the amount of food I eat from 30 years ago (50 lbs of fish), and yet, the food prices have risen exorbitantly and I can still afford it / spend less of my income on it... because I modified my food preferences.

In the end, (c) has both the amount and the type of food staying constant, so this is correct.

Other answers:
(d) This one is really tricky, but it's important to keep the bigger picture in sight. If the prices of nonfood items have risen faster than the price of food, and I am definitely spending more of my income to nonfood items than 30 years ago, it could STILL be that I am eating less or eating something else, which explains why I am spending less of my income on food. Food prices might still be rising at the same or higher rate that income is rising.
(e) I ignored this originally because it had "families" in it, but I think it's also wrong for a deeper reason. If families spend the same percentage of their income on food, and we assume that families and single persons don't eat SUCH different foods, then this weakens any conclusion about food prices changes -- because why haven't we seen that across the board? Then we're led to believe that maybe it's not about food prices, which is supposed to affect both families and single persons, but it's something else - single persons eating less or changing their eating habits, etc.

*Not sure how we could do this question in under 2 minutes during the actual test, but I would think: (e) has families, ignore. (b) directly undermines, ignore. (d) is tricky, can't really see how this would justify the conclusion or not, ignore. Between (a) and (c), (c) seems more specific to the stimulus and encompasses a part of (a) in it: "the same quantities" ~ "amount of food per capita." Choose (c), since it makes everything from 30 years ago to today CONSTANT. That's how I intuitively chose (c) during my run-through. Hope this helped someone.