The population of Liechtenstein (2001 estimate) is 32,528 (about one-third of whom are resident aliens), with an overall density of 203 persons per sq km (527 per sq mi). The capital and principal urban center is Vaduz (population, 1999, 5,106). German is the official language, but a dialect, Alemannish, is spoken commonly. Approximately 88 percent of the population is Roman Catholic. In 1991 primary school enrollment totaled 1,985 pupils; about 1,200 pupils attended secondary schools. Primary and secondary education is free in Liechtenstein; schooling is compulsory for 8 years.