Municipality Semič, which is part of the Jugovzhodna Slovenija statistical region, measures 147 km2; this ranks it 42th among Slovene municipalities.
Statistical data for 2015 reveal the following:
In the middle of 2015 about 3,800 people (about 1,950 men and 1,850 women) were living in the municipality, which ranks Semič 133th among Slovene municipalities. The population density was 26 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 –0.5 (in Slovenia 0.4). 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 –4.2. The sum of natural increase and net migration per 1,000 population in the municipality was negative. It was –4.8 (in Slovenia 0.6).
The mean age of people in Semič was 43.1 years, which was higher than the national average (42.6).
As in most Slovene municipalities, in Semič the number of old people was higher than the number of young people: there were 121 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 123. It also shows that the mean age of people in Sežana 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 Semič – as in most Slovene municipalities – more women were 65+ years old than 14 or less; for men the situation was the same.
In the school year 2015/2016 basic schools in Semič were attended by about 300 pupils, while various upper secondary schools were attended by about 150 pupils. There were 40 students and 11 graduates per 1,000 people in the municipality; in Slovenia the averages were 39 per 1,000 and 9 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 more than the national average (58%).
The registered unemployment rate was 15.6%, which is more than the national average (12.3%). As in most Slovene municipalities, more women than men were unemployed.
In Semič, average monthly gross earnings per person employed by legal persons were about 19% lower than the annual average of monthly earnings for Slovenia; and net earnings about 5% lower.
In 2015, there were 463 dwellings per 1,000 population. About 60% of dwellings had at least three rooms. Average size of dwellings in the municipality was 80 m2.
Every other person in Semič had a car (52 passenger cars per 100 population); cars in this municipality were on average 10.8 years old.
In 2015, 237 kg of municipal waste per person was collected in Semič, which is 78 kg less than on average in Slovenia.