6. Portugal
Increase: 266%
In 2010, there were 30, 000 Muslims in Portugal who accounted for less than 1% of the population. Estimates show that their number will be 110,000 in 2015, accounting for 1.3% of all residents. One of the major changes in religious distribution in Portugal will be a significant fall of Christian population which will decrease by 23.5%. Despite the decline, Christianity will remain dominant religion with 7.5 million followers.