The report, "Belief About God Across Time and Countries," found 13 percent of people living in the former East Germany expressed belief in God, while at the high end 94 percent of Filipinos say they have always been believers. The report said researchers found belief in God is higher among older people regardless of where they live.
"Belief in God has decreased in most countries, but the declines are quite modest especially when calculated on a per annum basis," said Tom W. Smith, director of the General Social Survey of the social science research organization NORC at the University of Chicago.
The data came from 30 countries in which surveys about belief in God have been taken at least twice since 1991.
The study found atheism is strongest in northwest European countries and the former Soviet states, with the exception of Poland. Belief was found to be increasing in Russia, Slovenia and Israel.
On average, 43 percent of those 68 and older are certain God exists, compared with 23 percent of those 27 and younger, the report said.
"Looking at differences among age groups, the largest increases in belief in God most often occur among those 58 years of age and older," Smith said. "This suggests that belief in God is especially likely to increase among the oldest groups, perhaps in response to the increasing anticipation of mortality."
In the United States, 81 percent of those surveyed said they have always believed in God. The report said 54 percent of Americans younger than 28 said they were certain of God's existence, compared with 66 percent of the people 68 and older.