Municipality Trebnje, which is part of the Jugovzhodna Slovenija statistical region, measures 163 km2; this ranks it 34th among Slovene municipalities.
Statistical data for 2015 reveal the following:
In the middle of 2015 about 12,200 people (about 6,250 men and 6,000 women) were living in the municipality, which ranks Trebnje 43th among Slovene municipalities. The population density was 75 people per square kilometre, which was lower than the national average of 102 people per square kilometre.
The number of live births was higher than the number of deaths, which means that natural increase per 1,000 population in the municipality was positive. It was 1.1 (in Slovenia 0.4). The number of people who moved from the municipality was lower than the number of people who moved into the municipality, so net migration per 1,000 population in the municipality was positive. It was 12.8. The sum of natural increase and net migration per 1,000 population in the municipality was positive. It was 13.9 (in Slovenia 0.6).
The mean age of people in Trebnje was 40.8 years, which was lower than the national average (42.6).
in contrast to most Slovene municipalities, in Trebnje the number of young people was higher than the number of old people: there were 91 people, aged 65 or more, per 100 people aged 0–14. This ratio shows that the value of the ageing index was lower than the national average of 123. It also shows that the mean age of people in Trzin is growing more slowly than in Slovenia as a whole. Data by sex show that the ageing index for women was in all Slovene municipalities higher than the ageing index for men. In Trebnje – as in most Slovene municipalities – more women were 65+ years old than 14 or less; for men the situation was exactly the opposite.
In the school year 2015/2016 basic schools in Trebnje were attended by about 1,100 pupils, while various upper secondary schools were attended by about 500 pupils. There were 40 students and 12 graduates per 1,000 people in the municipality; in Slovenia the averages were 39 per 1,000 and 9 per 1,000, respectively.
Among people aged 15–64 (i.e. working age population) about 66% were persons in employment (i.e. persons in paid employment or self–employed persons), which is more than the national average (58%).
The registered unemployment rate was 9.2%, which is less than the national average (12.3%). As in most Slovene municipalities, more women than men were unemployed.
In Trebnje, average monthly gross earnings per person employed by legal persons were about 10% lower than the annual average of monthly earnings for Slovenia; and net earnings about 6% lower.
In 2015, there were 401 dwellings per 1,000 population. About 62% of dwellings had at least three rooms. Average size of dwellings in the municipality was 84 m2.
Every other person in Trebnje had a car (56 passenger cars per 100 population); cars in this municipality were on average 9.8 years old.
In 2015, 252 kg of municipal waste per person was collected in Trebnje, which is 63 kg less than on average in Slovenia.