Happiness Research: A Review --from a viewpoint of low fertility in Japan(in Japanese)

At the beginning of our research, "Happiness in Having Children", we summarize precedent researches on happiness to answer to question, "What is Happiness?" We first compose happiness concept, and survey precedent researches on the factors which affect a feeling of happiness. The survey result concerning a decrease in the birthrate is mainly as follows: (1) Although the individual degree of happiness rises when income increase, the saturation point will be observed if it exceeds a certain point. It is because people refer to the relative income, not the absolute income (hedonic tread mill effect). (2) The degree of happiness becomes U shape as age goes up. (3) The degree of happiness of the person who lost his job is low. On the other hand, the degree of happiness of a person with a high stress of work is low. (4) A married person's degree of happiness is higher than an unmarried person. However, the gap between married person's degree of happiness and unmarried person's degree of happiness is shrinking in recent years. (5) When a child is born and a child-rearing start, especially a mother undertakes those burdens greatly, the degree of marital happiness falls. (6) Parents receive positive influence from a child through child-rearing. Moreover, a couple with a child is seldom divorced. (7) The degree of marital happiness is declining when a dual earner couple has more children.