Municipality Postojna, which is part of the Notranjsko-kraška statistical region, measures 270 km2; this ranks it 13th among Slovene municipalities.
Statistical data for 2011 reveal the following:
In the middle of 2011 about 15,700 people (about 7,850 men and 7,850 women) were living in the municipality, which ranks Postojna 31st among Slovene municipalities. The population density was 58 people per square kilometre, which was lower than the national average of 101 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 4.5 (in Slovenia 1.6). The number of people who moved from the municipality was higher than the number of people who moved into the municipality, so net migration per 1,000 population in the municipality was negative. It was -3.4. The sum of natural increase and net migration per 1,000 population in the municipality was positive. It was 1.1 (in Slovenia 2.6).
The mean age of people in Postojna was 41.1 years, which was lower than the national average (41.8).
In contrast to most Slovene municipalities, in Postojna the number of young people was higher than the number of old people: there were 99 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 117. It also shows that the mean age of people in Postojna 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 Postojna – as in most Slovene municipalities – more women were 65+ years old than 14 or less; for men the situation was exactly the opposite.
Postojna had 5 kindergartens. They were attended by 634 children or 73% of all children aged 1–5, which was less than the national average of 76%. In the school year 2011/2012 basic schools in Postojna were attended by about 1,220 pupils, while various upper secondary schools were attended by about 610 pupils. There were 50 students and 11 graduates per 1,000 people in the municipality; in Slovenia the averages were 51 per 1,000 and 10 per 1,000, respectively.
Among people aged 15–64 (i.e. working age population) about 61% were persons in employment (i.e. persons in paid employment or self-employed persons), which is more than the national average of 58%.
The registered unemployment rate was 10.4%, which is less than the national average (11.8%). As in most Slovene municipalities, more women than men were unemployed.
In Postojna, average monthly gross earnings per person employed by legal persons were about 6% lower than the annual average of monthly earnings for Slovenia; and net earnings about 4% lower.
Every 22nd person in the municipality was receiving at least one financial social assistance. In Slovenia as a whole every 24th person received at least one financial social assistance.
In 2011, there were 427 dwellings per 1,000 population. About 59% of dwellings had at least three rooms. Average size of dwellings in the municipality was 80 m2.
About every other person in Postojna had a car (54 passenger cars per 100 population); cars in this municipality were on average 9 years old.
In tourist accommodations in the municipality around 33,600 arrivals and 46,000 overnight stays of tourist were recorded, which is approximately 1.0% of all arrivals and 0.5% of all overnight stays of tourist in Slovenia.
In 2011, 367 kg of municipal waste per person was collected in Postojna, which is 15 kg more than on average in Slovenia.