I realize that this has been discussed elsewhere on the site, but I was interested in the use of the preposition "among" in a sentence from a story in yesterday's New York Times:
Research done by Emmanuel Saez, left, and Thomas Piketty has shown that inequality among the middle class and the rich is nearly as acute as it was before the Great Depression.
My first impression was that the sentence was incorrect, and that "between" should have been used instead. After thinking about it for a minute, however, it seems like the use of either preposition may be valid, but that the sentence would mean different things depending on the choice. With "between", the sentence is referring to inter-group differences between the incomes of the rich and the middle class. With "among", the sentence is referring to intra-group differences in income among the individual members of each particular group.
Honestly I have no idea if this interpretation is correct. Can someone please clarify this for me?