Since 1990, the Human Development Index (HDI) has been used by the United Nations to rank countries into four tiers of human development. Using data from the 2010 Human Development Report, this study has analyzed the mean life satisfaction of citizens from 144 countries that are at different levels of HDI. Simple regression analysis shows that HDI alone accounts for 63% of the variation in the mean life satisfaction across the countries. A strong positive correlation has been shown to exist between life satisfaction and HDI. However, countries with about the same level of HDI can have vastly different life satisfaction. Results from the Multiple Regression Analysis indicate that part of the variations in life satisfaction in countries with ...