The ratio of women per 1,000 men was 1,102. The birth rate per 1000 people was 12.3 per mile and steadily increasing in the last 5 years, the death rate reaching 12.1 per mile and decreasing. The natural growth rate during 2009 was 0.2 per mile, the first positive growth rate in nearly 20 years. The considerable immigration to the capital from poorer regions of the country, as well as urbanisation, are among the other reasons for the increase in Sofia's population. The infant mortality rate was 5.6 per 1,000, down from 18.9 in 1980. According to the 2011 census, people aged 20–24 years are the most numerous group, numbering 133,170 individuals and accounting for 11% of the total 1,202,761 people. The median age is 38 though. According to the census, 1,056,738 citizens (87.9%) are recorded as ethnic Bulgarians, 17,550 (1.5%) as Romani, 6,149 (0.5%) as Turks, 9,569 (0.8%) belonged to other ethnic groups, 6,993 (0.6%) do not self-identify and 105,762 (8.8%) remained with undeclared affiliation.