The Church blames this trend, seen in many parts of Europe, on a shift in lifestyle and increasing secularisation.
The report says that 73.8% Slovenian residents (1,523,000 out of 2,062,700) were Catholics in 2014. The figure is however quite different from the 2004 census, when 81 % residents said they were Catholics.
A comparison between 2004 and 2014 shows that the number of Catholics dropped by just under 6 percentage points (pps), according to the Church data, which is based on its data for christenings and other sacraments.
In the same period, the number of christenings went down by 12pps, despite an increase in the number of births. Despite the drop, some 60% of all children born in Slovenia are Christened, according to the report.
The number of people opting for other sacraments, including communion, confirmation and church wedding, is on the decline as well. The report shows that some 40% of couples opt for a church wedding.
While the report points to a decrease in the number of priests, there is an increase in laypersons helping out more than 1,000 members of the clergy across the country.
Currently, there are 785 parishes in Slovenia, headed by some 1,050 priests and eleven bishops. The Church owns more than 2,900 churches, chapels and other sacral landmarks such as crosses across Slovenia.
The Church-owned buildings make up 80% of all heritage-listed buildings in the country, the report says, adding that the Church on the other hand gets only 5.9% of total heritage preservation funds from the state.
The report also shows that donations by believers are the main funding source for the Church.
The report underlines that religious activities of the Church are not supported by the government, while activities beneficial to the community are funded by the state.
The state does however contribute to the social security of priests, having paid in EUR 1.6m for this purpose in 2014. On the other hand, the Church paid EUR 16m in various taxes, such as property and forest taxes, the report adds.