In 2006, 2007, and 2008, Gallup asked representative samples in 143 countries and territories whether religion was an important part of their daily lives. The accompanying map shows religiosity by country, ranging from the least religious to the most religious on a relative basis. Across all populations, the median proportion of residents who said religion is important in their daily lives is 82%.
Gallup’s World Poll, indicates that 8 of the 11 countries in which almost all residents (at least 98%) say religion is important in their daily lives are poorer nations in sub-Saharan Africa and Asia. On the opposite end of the spectrum, the 10 least religious countries studied include several with the world’s highest living standards, including Sweden, Denmark, Norway, Hong Kong, and Japan.
Among 27 countries commonly seen as part of the developed world, the median proportion of those who say religion is important in their daily lives is just 38%.
Obviously, these data only compare the importance of religion in people’s lives — they say nothing about what being highly religious means in different parts of the world and among different faiths.