Children as young as one year old can be enrolled in the kindergartens though this is not compulsory. Most of the 450 kindergartens are state run and integrated with primary schools and some are privately run.
The population of Croatia in 2003 was estimated by the United Nations at 4,428,000, which placed it as number 115 in population among the 193 nations of the world. In that year approximately 13% of the population was over 65 years of age, with another 20% of the population under 15 years of age.
Croatia's rivers belong to the Adriatic and the Black Sea basin. The rivers in the interior are large and calmer (Sava, Drava, Danube).