Municipality Idrija, which is part of the Goriška statistical region, measures 294 km2; this ranks it 8th among Slovene municipalities.
Statistical data for 2018 reveal the following:
In the middle of 2018 about 11,730 people (about 5,890 men and 5,840 women) were living in the municipality, which ranks Idrija 45th among Slovene municipalities. The population density was 40 people per square kilometre, which was lower than the national average of 102 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 -4.8 (in Slovenia -0.4). 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 4.1. The sum of natural increase and net migration per 1,000 population in the municipality was negative. It was -0.7 (in Slovenia 6.8).
The mean age of people in Idrija was 44.8 years, which was higher than the national average (43.3).
As in most Slovene municipalities, in Idrija the number of old people was higher than the number of young people: there were 155 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 131. It also shows that the mean age of people in Idrija is growing more rapidly than in Slovenia as a whole. Data by sex show that the ageing index for women was in this municipality higher than the ageing index for men. In Idrija – as in most Slovene municipalities – more women were 65+ years old than 14 or less; for men the situation was the same.
Idrija had 5 kindergartens. They were attended by 486 children or 81% of all children aged 1–5, which was the same as the national average. In the school year 2018/19 elementary schools in Idrija were attended by about 1,070 pupils, while various upper secondary schools were attended by about 430 pupils. There were 38 students and 8 graduates per 1,000 people in the municipality; in Slovenia the averages were 37 per 1,000 and 8 per 1,000, respectively.
Among people aged 15–64 (i.e. working age population) about 72% were persons in employment (i.e. persons in paid employment or self-employed persons), which is more than the national average (65%).
In Idrija, average monthly gross earnings per person employed by legal persons were about 3% higher than the annual average of monthly earnings for Slovenia; and net earnings about 3% higher.
In 2018, there were 420 dwellings per 1,000 population. About 68% of dwellings had at least three rooms. Average size of dwellings in the municipality was 80 m2.
More than every other person in Idrija had a car (54 passenger cars per 100 population); cars in this municipality were on average 10 years old.
In 2018, 361 kg of municipal waste per person was collected in Idrija, which is the same as on average in Slovenia.