Some of the most prosperous nations in the world have experienced a pr

(A) It fail to specify the many reasons younger people have for saving money, and it fails to identify which of those reasons is the strongest. -- We do not really care about the quality of the reasons. Even if this were true, saying that the reason is not good enough does not help in pointing out an error.

(B) It assumes that a negative savings rate—the result of the average household’s spending all of its after-tax income as well as some of its existing savings—cannot ever come about in any nation. -- Completely out of scope. Lets say there can be a negative rate - Great! - Lets also say there cant be one - Great! - Does it really matter?

(C) It fails to cite statistics showing that the average age of the population of certain nations is rising. We believe everything that is there in the question stem.

(D) It only takes into account the comparative number of reasons older and younger people, respectively, have for saving, and not the comparative strength of those reasons. - CORRECT - It clearly says that the NUMBER of reasons to save is less for elder people. Lets say healthcare is costly - this alone could mean they save 100 and a young person would save only 30. Thus there is an apparent flaw.

(E) It uses after-tax income as the base for computing the national savings rate without establishing by argument that after-tax income is a more appropriate base than before-tax income. - Nonsensical statement.