People in Developing Countries Happier; Developed Less Happy (C&Others)

111126 With the economic growth, more people are richer than before. In developing countries, people are happier than before, however in developed countries, people are no happier than they used to be. Why people are happier or less happy than before?

151114 Economic growth in in recent years made some people in both developed countries and developing countries richer. However, research showing that while people in developing countries are happier, people in developed countries seems no happier than before. Why? What can we learn from it?