The rapid development of China's economy first guarantees the material factors for the happiness of residents. The income of urban and rural residents has steadily increased, and the physical fitness and life span of residents have increased. In the market economy system, material resources are extremely rich, and people can give play to their initiative and come to Get the greatest material enjoyment. The total retail sales of consumer goods in urban and rural areas has steadily increased, indicating that the living standards of residents are improving. These are the ignorance guarantees for people to maintain happiness. However, the reality also tells us that many middle-class and even wealthy people with rich incomes It is also often easier to "depress" than the working class. Of course, this is not because "rich" makes people unhappy, but because "not bad money" makes a happy growth point of material richness disappear. What does this text mean? ["China's working class is happier than the middle and wealthy classes.", 'Most billionaires are unhappy.', 'Material wealth is the basic guarantee of happiness, but the happiness experience it can bring is not sustainable.', 'The degree of happiness is directly proportional to the amount of wealth.']