Municipality Kostel, which is part of the Jugovzhodna Slovenia statistical region, measures 56 km2; this ranks it 123th among Slovene municipalities.
Statistical data for 2008 reveal the following:
At the end of 2008 about 600 people (about 300 men and 300 women) were living in the municipality, which ranks Kostel 206th among Slovene municipalities. The population density was 12 people per square kilometre, which was lower than the national average of 100 people per square kilometre.
The number of live births was lower than the number of deaths, which means that natural increase per 1,000 population in the municipality was negative. It was -4.6 (in Slovenia 1.7). 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 -24.6. The sum of natural increase and net migration per 1,000 population in the municipality was negative. It was -29.2 (in Slovenia 10.9).
The mean age of people in Kostel was 48.1 years, which was higher than the national average (41.3 years).
As in most Slovene municipalities, in Kostel the number of old people was higher than the number of young people: there were 255 people, aged 65 or more, per 100 people aged 0–14. This ratio shows that the value of the ageing index was higher than the national average of 118. It also shows that the mean age of people in Kostel is growing more rapidly 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 Kostel – as in most Slovene municipalities – more women were 65+ years old than 14 or less; for men the situation was the same.
Kostel had 1 kindergarten. It was attended by 18 children. Of all children aged 1–5, 93% were included in kindergartens, which was more than the national average of 70%. In the school year 2008/09 elementary school in Kostel was attended by about 40 pupils. About 10 pupils from the municipality attended various secondary schools. There were 40 students and 8 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 61% were persons in employment (i.e. persons in paid employment or self-employed persons), which is less than the national average of 62%.
The registered unemployment rate was 10.0%, which is more than the national average (6.7%). As in most Slovene municipalities, more women than men were unemployed.
In Kostel, average monthly gross earnings per person employed by legal persons were about 12% lower than the annual average of monthly earnings for Slovenia; and net earnings about 10% lower.
Every 22nd 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.
In 2008, there were 913 dwellings per 1,000 population. About 46% of dwellings had at least three rooms. Average size of dwellings in the municipality was 67 m2.
Every other person in Kostel had a car (48 passenger cars per 100 population); cars in this municipality were on average 8 years old.
In 2008, 314 kg of municipal waste per person was collected in Kostel, which is 105 kg less than on average in Slovenia.