Income and the happiness is always high correlation. Simple example is that people will be unhappy when they are hurgry or thristy. Only for the mentally disorder person could not apply for the case, and the presumtion is that people is pursuing for live not dead. According to the Moslow's theory, people will pursue for higher mental need such as fume, money, social status and Self satisfaction only if they fulfill the basic need. And money, to a large extend, can absolutely solve our food problem. Therefore, i can assure that high income is the fundamental criteria of having happiness. However, why are many people not happy?! I think it is possibly that people do too much comparison with others and don't smart enough to discover the merit themselve. Thank you@