In Argonia the average rate drivers pay for car accident insurance is

Insurance = not based on distance driven
Therefore, those who drive less partially subsize the cost of those who drive more
　　
Use the Assumption Negation for (B) the ave. cost of insurance for those who drive less is equal average cost of those who drive more.
The argument will fall apart if this assumption is false. If the cost are just the same, then "partial subsidy" is not going to happen.

（A） the average accident insurance rate for all drivers rises whenever a substantial number of new drivers buy insurance
substantial new drivers causing increase in insurance rate is not anywhere in the argument; no tie to the conclusion

（C） the lower the age of a driver， the higher the insurance rate paid by that driver
age is not relevant to the conclusion

（D） Insurance company profits would rise substantially if drivers were classified in terms of the actual number of miles they drive each year
future prediction is not claimed anywhere in the argument

（E） Drivers who have caused insurance companies to pay costly claims generally pay insurance rates that are equal to or lower than those paid by other drivers
we need an assumption for those who drive less and drive more

In Argonia the average rate drivers pay for car accident insurance is regulated to allow insurance companies to make a reasonable profit. Under the regulations, the rate any individual driver pays never depends on the actual distance driven by that driver each year. Therefore， Argonians who drive less than average partially subsidize the insurance of those who drive more than average.
　　
The conclusion above would be properly drawn if it were also true that in Argonia
　　
（A） the average accident insurance rate for all drivers rises whenever a substantial number of new drivers buy insurance – IMO POE does not immediately eliminate this. But logically, here, we are discussing about the ones who drive more miles and the ones who drive less. So this statement is not relevant.
（B） the average cost to insurance companies of insuring drivers who drive less than the annual average is less than the average cost of insuring drivers who drive more than the annual average. On hold.
（C） the lower the age of a driver， the higher the insurance rate paid by that driver – Goes out in the the first instance of POE application.
（D） Insurance company profits would rise substantially if drivers were classified in terms of the actual number of miles they drive each year- On hold.
（E） Drivers who have caused insurance companies to pay costly claims generally pay insurance rates that are equal to or lower than those paid by other drivers. Goes out in the the first instance of POE application.

I was stuck between B&D. Chose D instead of B, the OA. In hindsight B looks to support the Argument more directly compared to D, which is generic.

Insurance rate is fixed irrespective of the distance driven.This method allows ins co. to make profit.
Those who drive more also pay subsidized amount as compared to less driven.

All these conditions are fulfilled only when option B is satisfied.

How could I know to which level (500, 600, etc) does this question fit in?

I suggest you go through these posts -

1. GMAT Critical Reasoning Question Directory by Topic & Difficulty

2. 150 Hardest Critical Reasoning Questions

These will give you an idea...

another assumption can be made is an assumption about the insurance price paid by drivers. Surely, that assumption has the same idea with the assumption in this question.

　　
（A） the average accident insurance rate for all drivers rises whenever a substantial number of new drivers buy insurance

（B） the average cost to insurance companies of insuring drivers who drive less than the annual average is less than the average cost of insuring drivers who drive more than the annual average

（C） the lower the age of a driver， the higher the insurance rate paid by that driver

（D） Insurance company profits would rise substantially if drivers were classified in terms of the actual number of miles they drive each year

（E） Drivers who have caused insurance companies to pay costly claims generally pay insurance rates that are equal to or lower than those paid by other drivers


Only B talks about "average cost and the driving distance"

Kindly explain how B is right answer and E is not.

A. the average accident insurance rate for all drivers rises whenever a substantial number of new drivers buy insurance - this does not explain the conclusion.

B. the average cost to insurance companies of insuring drivers who drive less than the annual average is less than the average cost of insuring drivers who drive more than the annual average - we can infer from this that since the insurance cost incurred on insuring drivers who drive less than the annual average, the insurance company has more funds that it can allocate to drivers who drive more than the annual average. If the latter receives more financial support (in terms of reimbursements) from the insurance companies, then these drivers end up paying less from their pockets. (B) is therefore necessary to establish the conclusion. Hence, (B) is the right answer choice.

C. the lower the age of a driver， the higher the insurance rate paid by that driver - irrelevant.

D. Insurance company profits would rise substantially if drivers were classified in terms of the actual number of miles they drive each year - the conclusion is not concerned with 'how to increase' profitability of insurance companies.

E. Drivers who have caused insurance companies to pay costly claims generally pay insurance rates that are equal to or lower than those paid by other drivers - irrelevant to the conclusion drawn.

This is a support the conclusion question.

Conclusion: Avg. Insurance rate (IR) for people who drive less is lower than those who drive more. But premise also states that insurance rate is NOT dependent on distance driven.

A. the average accident insurance rate for all drivers rises whenever a substantial number of new drivers buy insurance
--> This just states that average IR rises for everyone if new people sign up. Irrelevant. Discard

B. the average cost to insurance companies of insuring drivers who drive less than the annual average is less than the average cost of insuring drivers who drive more than the annual average
--> If IR is higher for people who drive more although it doesnt depend on distance (acc to regulation), this option states the reason--> It's due to the cost of getting the drivers insured on the company's side

C. the lower the age of a driver， the higher the insurance rate paid by that driver
--> Discard, nothing to do with the premise or conclusion

D. Insurance company profits would rise substantially if drivers were classified in terms of the actual number of miles they drive each year
-->Attacks the premise, discard!

E. Drivers who have caused insurance companies to pay costly claims generally pay insurance rates that are equal to or lower than those paid by other drivers
--> Has nothing to do with premise/conclusion. Discard!

I couldn't find any explanations that makes sense to me under this problem. So here is my take:

(B) The average cost to insurance companies of insuring drivers who drive less than the annual average is less than the average cost of insuring drivers who drive more than the annual average.

It is very important to understand that the drivers who drive less and the ones who drive more pay about the same rate! How do we know that? -->

From stimulus, we know government regulate the insurance rates, and the rates are never dependent on mileage. THEREFORE, the drivers who drive less and the ones who drive more will either both have the same rate or have different rates based on other factors (car models, years, driver age etc.). However, the later one (car models, years, driver age etc.) is irrelevant in this problem. Therefore, we can assume that they have about the same rate!

(tbh, I feel that this is too much to think about especially when you are taking the actual test. But you can always approach to this answer by POE. But what I just said above is only for the sake of explaining this specific problem since I was really confused about this answer as well.)

Come back to the answer choice. Now we know two groups cost the same. And note that the average cost here is for the insurance companies not the customers! Therefore, from insurance companies' standpoint, let's say the cost for drivers who drive less is 100, but the cost for companies are 40. Then they would save the 60 bucks and use it on insuring the drivers who drive more. The drivers who drive less are indirectly subsidizing the people who drive more.

(E) Drivers who have caused insurance companies to pay costly claims generally pay insurance rates that are equal to or lower than those paid by other drivers.

I chose this one at first. And this is how I understand it now:

From my analysis above about B, we get that two kinds of drivers cost about the same (which makes this choice wrong). BUT let's say you didn't know that when you are working on this problem:

Do we have to assume this? Negating this, drivers who drive pay more pay higher than those who drive less. However, even if drivers who drive more are paying more, that doesn't necessarily mean that the drivers who drive less are not subsidizing --> Negating this doesn't weaken the conclusion! Let's put them into simple figures:



Drivers who drive more are paying higher than the ones who drive less (negation example of E), and at the same time, cost to insurance companies on insuring those who drive more are a lot higher than those who drive less. From this table, we can tell the subsidizing thing actually does take place! Negation of E doesn't weaken the conclusion --> E is wrong.

(E) Drivers who have caused insurance companies to pay costly claims generally pay insurance rates that are equal to or lower than those paid by other drivers.

We are concerned with the drivers who drive less and those who drive more. Option E focuses on different kind of drivers. That's why E is incorrect.

I selected E at first. Then later realised beautiful word play of B. Here' my take on option B and why it is correct.(I never understood any of the above explanations)

we are told 1: "Argonians who drive less than average partially subsidise the insurance of those who drive more than average."
and
we are told 2: "insurance companies make reasonable profit."

=> we can say : those who drive less->pay more to insurance companies and who drive more->pay less.

B says that "cost to insurance companies from those who drive less is less than those who drive more" means those who drive less have minor damage so cost to insurance company is less and eventually they make more profit. Likewise we can say those who drive more have major damage, so cost to insurance company is more.

=> "Argonians who drive less than average partially subsidise the insurance of those who drive more than average."

This is a good question.

Conclusion: Argonians who drive less than average partially subsidize the insurance of those who drive more than average.
Evidence: The rate any individual driver pays never depends on the actual distance driven by that driver each year.

Now why is the author concluding that drivers who drive less are subsidizing the insurance premium for those who drive less? I can only assume this when I know that the costs of servicing is lower for those who drive less.

For instance:
Say X and Y both invest $100 and $1000 resp in shares through a wealth manager (WM). The WM charges a fixed fee of $10 each account. When can we say that X is kind of subsidizing the fees for Y? Only when the costs for servicing X ($4) is lower than Y ($6). Think about it. Because cost of servicing X is lower so premium for X should have been lower but she is paying more. Why? Because it helps the WM to balance the costs.

Now assume, the costs of servicing were same for X, then the same premium is justified. If the cost of servicing is higher for X than for Y, Y is subsidizing the payment for X.

Only B is the relevant choice which addresses this issue and relates to the right segments (who drive more and who drive less).
Let's negate the choice:

(B) The average cost to insurance companies of insuring drivers who drive less than the annual average is equal /more than the average cost of insuring drivers who drive more than the annual average.
My conclusion is no longer valid. If the cost is higher for insuring drivers who drive less, then they are not subsidizing the premium paid by drivers who drive more. They are paying higher because the cost to service them is higher.

E was a contender for me at first.

(E) Drivers who have caused insurance companies to pay costly claims generally pay insurance rates that are equal to or lower than those paid by other drivers.

We are just concerned with the premium amounts and not the claims.
Negate: Drivers who have caused insurance companies to pay costly claims generally do not pay insurance rates that are equal to or lower than those paid by other drivers.
Here the argument is who drives less and who drives more and not about who takes more claims and who takes less. The segment is different.