University of Leicester psychologist Adrian White pooled data from over 100 studies that looked at self-reported happiness all over the world. The result is a global projection of subjective well-being that ranks 178 countries according to how satisfied their residents are with their lives. White also compared satisfaction scores with GDP, life expectancy, and access to education in each country. Life expectancy was most tightly linked to happiness, suggesting that health may be the biggest factor in contentment. Income showed the next strongest correlation, followed closely by education.