Municipality Postojna, which is part of the Notranjsko-kraška statistical region, measures 270 km2; this ranks it 13th among Slovene municipalities.
Statistical data for 2012 reveal the following:
In the middle of 2012 about 15,750 people (about 7,900 men and 7,900 women) were living in the municipality, which ranks Postojna 32th 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 2.0 (in Slovenia 1.3). 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 0.5. The sum of natural increase and net migration per 1,000 population in the municipality was positive. It was 2.5 (in Slovenia 1.6).
The mean age of people in Postojna was 41.1 years, which was lower than the national average (42).
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 118. 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 671 children or 71% of all children aged 1–5, which was less than the national average of 75%. In the school year 2012/2013 basic schools in Postojna were attended by about 1,240 pupils, while various upper secondary schools were attended by about 590 pupils. There were 40 students and 11 graduates per 1,000 people in the municipality; in Slovenia the averages were 47 per 1,000 and 10 per 1,000, respectively.
Among people aged 15–64 (i.e. working age population) about 60% were persons in employment (i.e. persons in paid employment or self-employed persons), which is more than the national average of 57%.
The registered unemployment rate was 11.4%, which is less than the national average (12%). In contrast to most Slovene municipalities, more men than women were unemployed.
In Postojna, average monthly gross earnings per person employed by legal persons were about 8% lower than the annual average of monthly earnings for Slovenia; and net earnings about 6% lower.
In 2012, there were 428 dwellings per 1,000 population. About 59% of dwellings had at least three rooms. Average size of dwellings in the municipality was 81 m2.
About every other person in Postojna had a car (55 passenger cars per 100 population); cars in this municipality were on average 9 years old.
In 2012, 368 kg of municipal waste per person was collected in Postojna, which is 41 kg more than on average in Slovenia.