Municipality Kostel, which is part of the Jugovzhodna Slovenija statistical region, measures 56 km2; this ranks it 123rd among Slovene municipalities.
Statistical data for 2011 reveal the following:
In the middle of 2011 about 650 people (about 350 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 101 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 -15.4 (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 -29.2. The sum of natural increase and net migration per 1,000 population in the municipality was negative. It was -44.5 (in Slovenia 2.6).
The mean age of people in Kostel was 49.0 years, which was higher than the national average (41.8).
As in most Slovene municipalities, in Kostel the number of old people was higher than the number of young people: there were 261 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 117. 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 13 children or 87% of all children aged 1–5, which was more than the national average of 76%. In the school year 2011/2012 basic school in Kostel was attended by about 40 pupils, while various upper secondary schools were attended by about 10 pupils. There were 30 students and 6 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 54% were persons in employment (i.e. persons in paid employment or self-employed persons), which is less than the national average of 58%.
The registered unemployment rate was 15.6%, which is more than the national average (11.8%). 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 25th 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 968 dwellings per 1,000 population. About 54% of dwellings had at least three rooms. Average size of dwellings in the municipality was 72 m2.
Every other person in Kostel had a car (50 passenger cars per 100 population); cars in this municipality were on average 8 years old.
In 2011, 247 kg of municipal waste per person was collected in Kostel, which is 105 kg less than on average in Slovenia.