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The number of babies born to Muslim parents is expected to exceed the number born to Christian parents by 2035, putting Islam on course to be the world's biggest religion, according to a new study.

The number of people born with no religious affiliation is set to shrink, with the number of babies born to Christian or Muslim parents set to expand from 64% of the world's population in 2010-2015, to 71 per cent in 2055-2060, according to a report by Pew Research Center.

The study points to significant demographic shifts driven by regional trends in age and fertility, with the youthful Christian population of regions such as sub-Saharan Africa to rise, while the elderly Christian population of Europe is expected to decline in the decades ahead. In Germany, between 2010 and 2015, there were an estimated 1.4m more deaths than births among Christians.

The high birth rate among Muslims cements its status as the world's fastest-growing religion, with births to Muslims making up around 31% of total global births between 2010 and 2015, despite Muslims making up only around 24% of the global population.

The study projects that between 2030 and 2035, there will be 225m babies born to Muslims to 224m to Christians, despite Christians being the larger group. This gap will have stretched to 6m in the 2025-2060 period, the study predicts.

Overall, the world's Christian population is expected to continue growing, with Christian births making up 33% of the world's total, marginally higher than its 31% of the world's population between 2010 and 2015.

In contrast, the birth rate amongst atheist and agnostic parents is low. Only 10% of babies were born to religiously unaffiliated mothers between 2010 and 2016, with that group making up around 16% of the world's population. This explains why the study expects the birth rate amongst the religiously affiliated to fall to 9% between 2055 and 2060.

Religiously unaffiliated people are "heavily concentrated in places with ageing populations and low fertility, such as China, Japan, Europe and North America. By contrast, religions with many adherents in developing countries – where birthrates are high and infant mortality rates have been falling – are likely to grow quickly. Much of the worldwide growth of Islam and Christianity, for example, is expected to take place in sub-Saharan Africa," said Pew.

Pew's projections are based on the same data as was used in a 2015 Pew Research study in which it was predicted that Islam would become the world's biggest religion by 2075. They rely on data collected over the course of several years by 2,500 global censuses.