The final part of the Extreme World season in June 2011 examines the importance of religion in peoples' lives.

Extreme World is a new season of coverage on TV, Radio and Online, examining global differences. Over the next few months, BBC News correspondents will be exploring eight key themes that illustrate the divisions in our extreme world. Special Report: Extreme World

A Gallup survey found 84% of adults worldwide still view religion as an important part of their daily lives - unchanged for the past four years.

The survey which was conducted in 114 countries in 2009 showed that in 10 countries, including Bangladesh, Niger, Yemen and Indonesia, at least 98% of the population say religion is important in their daily lives.

Each of the most religious countries is relatively poor, with a per capita GDP below $5,000. By contrast, in countries with a much higher GDP per capita, only about 47% of the population say religion is important to them.

The least religious countries surveyed include, Estonia on 16%, Sweden on 17% and Denmark on 19%.

Three of the four lower-income countries regarded as least religious were formerly part of the Soviet Union, where religious expression was restricted until its collapse in 1991.

Even within the higher-income countries, belief varies widely. Americans generally place more importance on religion than Europeans, where church attendance is declining.

Within the US the significance of religion in daily life also varies widely. Residents of the southern state of Mississippi claim to be most religious - wtih 82% saying religion is very important in their lives - in the eastern state of New Hampshire, only 36% say religion is important to them.

Christianity, including the Catholic and Protestant churches, still claims to be the biggest religion in the world with about 2.1 billion followers or 32% of the world population. Islam is reported to have about 1.6 billion members, representing 23% of the world population in 2009.