A study by the Vienna-based WIREL project showed that in 30 years time only one third of the capital will be Catholic and the proportion of Muslims will almost double to 21 percent.
Researchers estimate that Vienna is currently around 41 percent Catholic, four percent Protestant, nine percent Orthodox (mainly Serbian), 12 percent Muslim and 0.5 percent Jewish. Three percent are other religions and 30 percent are atheist or agnostic.
Ramon Bauer from the WIREL project said that since the 1970s Viennese people have been leaving the Catholic church and increased migration has contributed to an increase in Orthodox Christians and Muslims.
“The trend is towards the privatization and individualization of religion,” Bauer said. He added that Vienna’s diverse religions is not typical of the rest of Austria’s states, where the Catholic church still plays a leading role.
One reason why the number of Muslims and Orthodox Christians is expected to rise in future is that they are seen as relatively “young” religions - with Muslim youth the most religious of their age group. The population of Orthodox Christians is expected to grow from nine to 11 percent.
The population of Catholics is predicted to sink to 33 percent.
“Future birth rates will play a role in the expansion of religions and religion tends to be inherited,” Bauer said. Muslim and Jewish women tend on average to have more children, he added.
He said there is also a trend towards interfaith partnerships in Vienna although religion will often play a less significant role and interfaith families tend to have less children.