It seems to be a very broad question. For the most part, the characters that change in Fitzgerald's work help to bring out the hollowness that might exist at the very heart of the American Dream. The pursuit of materialism and the attempt to emotionally engage upon such a foundation allows a view of the American Dream which raises questions about its usefulness. At the same time, the other level of change which happens concerns the entire social setting which is predicated upon the trappings of wealth and the desire to be "popular." At some level, the characters in the work show this sad nature. It acquires even greater significance as the Jazz Age ends and the Great Depression begins.