GMAT Critical Reasoning (CR) | A statistical review of word types and frequencies in all

D makes it likely that a selection effect is at work. Over time, books heavy on slang are weeded out, so that the older population of books becomes less and less slangy. As an analogy, think of the quality of books available in your local bookstore. It is likely to stock many recently-published books, regardless of quality. However, older books will only be in stock if they are good (or at least famous). This might make it appear that the literature of, say, the 1920's is superior to that of today,