At 1.3% per year as of 2008 data, ethnic Albanians in Kosovo have the fastest rate of growth in population in Europe. Over an 82-year period (1921–2003) the population of Kosovo grew to 460% of its original size. Whereas Albanians constituted 60% of Kosovo's 500,000 person population in 1931, by 1991 they reached 81% of Kosovo's 2 million person population. In the second half of the 20th century, Kosovo Albanians had three times higher birth rates than Serbs. In addition, most of Kosovo's pre-1999 Serb population relocated to Serbia proper following the ethnic cleansing campaign in 1999. Municipalities of Kosovo are largely rural, with only eight municipalities having more than 40,000 inhabitants living in the urban areas.