Municipality Mežica, which is part of the Koroška statistical region, measures 26 km2; this ranks it 188th among Slovene municipalities.
Statistical data for 2012 reveal the following:
In the middle of 2012 about 3,650 people (about 1,850 men and 1,800 women) were living in the municipality, which ranks Mežica 137th among Slovene municipalities. The population density was 138 people per square kilometre, which was higher 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 -2.5 (in Slovenia 1.3). 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 -0.8. The sum of natural increase and net migration per 1,000 population in the municipality was negative. It was -3.3 (in Slovenia 1.6).
The mean age of people in Mežica was 44.0 years, which was higher than the national average (42).
As in most Slovene municipalities, in Mežica the number of old people was higher than the number of young people: there were 142 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 Mežica 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 Mežica – as in most Slovene municipalities – more women were 65+ years old than 14 or less; for men the situation was the same.
Mežica had 1 kindergarten. They were attended by 143 children or 74% of all children aged 1–5, which was less than the national average of 75%. In the school year 2012/2013 basic school in Mežica was attended by about 270 pupils, while various upper secondary schools were attended by about 140 pupils. There were 40 students and 10 graduates per 1,000 people in the municipality; in Slovenia the averages were 47 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 57%.
The registered unemployment rate was 11.0%, which is less than the national average (12%). As in most Slovene municipalities, more women than men were unemployed.
In Mežica, average monthly gross earnings per person employed by legal persons were about 6% lower than the annual average of monthly earnings for Slovenia; and net earnings about 5% lower.
In 2012, there were 414 dwellings per 1,000 population. About 48% of dwellings had at least three rooms. Average size of dwellings in the municipality was 74 m2.
Every other person in Mežica had a car (48 passenger cars per 100 population); cars in this municipality were on average 9 years old.
In 2012, 279 kg of municipal waste per person was collected in Mežica, which is 48 kg less than on average in Slovenia.