Municipality Postojna, which is part of the Notranjsko-kraška statistical region, measures 270 km2; this ranks it 13th among Slovene municipalities.
Statistical data for 2008 reveal the following:
At the end of 2008 about 15,400 people (about 7,800 men and 7,600 women) were living in the municipality, which ranks Postojna 31st among Slovene municipalities. The population density was 57 people per square kilometre, which was lower than the national average of 100 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 3.2 (in Slovenia 1.7). 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 12.6. The sum of natural increase and net migration per 1,000 population in the municipality was positive. It was 15.8 (in Slovenia 10.9).
The mean age of people in Postojna was 40.8 years, which was lower than the national average (41.3 years).
As in most Slovene municipalities, in Postojna the number of old people was higher than the number of young people: there were 107 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 4 kindergartens. They were attended by 502 children. Of all children aged 1–5, 80% were included in kindergartens, which was more than the national average of 70%. In the school year 2008/09 elementary schools in Postojna were attended by about 1,200 pupils. About 630 pupils from the municipality attended various secondary schools. There were 60 students and 11 graduates per 1,000 people in the municipality; in Slovenia the averages were 55 per 1,000 and 8 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 of 62%.
The registered unemployment rate was 4.7%, which is less than the national average (6.7%). 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 4% lower than the annual average of monthly earnings for Slovenia; and net earnings about 3% lower.
Every 32nd person in the municipality was receiving at least one financial social assistance. In Slovenia as a whole every 28th person received at least one financial social assistance.
The value of gross investment in new fixed assets in the municipality (EUR 3,967 per capita) was higher than the national average (EUR 3,165 EUR per capita).
In 2008, there were 412 dwellings per 1,000 population. About 56% of dwellings had at least three rooms. Average size of dwellings in the municipality was 79 m2.
About every other person in Postojna had a car (52 passenger cars per 100 population); cars in this municipality were on average 8 years old.
In tourist accommodations in the municipality around 46,000 arrivals and 66,600 overnight stays of tourist were recorded, which is approximately 1.7% of all arrivals and 0.8% of all overnight stays of tourists in Slovenia.
In 2008, 508 kg of municipal waste per person was collected in Postojna, which is 89 kg more than on average in Slovenia.