− among the smallest proportions of any state in Germany). Nevertheless, the number rose from 33,000 in July 2011, an increase of 24% in only two years. About 4% of the population are migrants (including persons that already received the German citizenship). The biggest groups of foreigners by citizenship are (as of 2012): Russians (3,100), Poles (3,000), Turks (2,100) and Ukrainians (2,000). The number of foreigners varies between regions: the college towns Erfurt, Jena, Weimar and Ilmenau have the highest rates, whereas there are almost no migrants living in the most rural smaller municipalities. The Thuringian population has a significant sex ratio gap, caused by the emigration of young women, especially in rural areas. Overall, there are 115 to 120 men per 100 women in the 25–40 age group ("family founders") which has negative consequences for the birth ratio. Furthermore, the population is getting older and older with some rural municipalities recording more than 30% of over-65s (pensioners). This is a problem for the regional labour market, as there are twice as many people leaving as entering the job market annually. Natural and spatial tendencies The birth rate was about 1.8 children per women in the 1970s and 1980s, shrinking to 0.8 in 1994 during the economic crisis after the reunification and rose again to more than 1.4 children in 2010, which is a higher level than in West Germany. Nevertheless, there are only 17,000 births compared to 27,000 deaths per year, so that the annual natural change of the Thuringian population is about −0.45%. In 2015 there were 17.934 births, the highest number since 1990. Migration plays an important role in Thuringia. The internal migration shows a strong tendency from rural areas towards the big cities. From 2008 to 2012, there was a net migration from Thuringia to Erfurt of +6,700 persons (33 per 1000 inhabitants), +1,800 to Gera (19 per 1000), +1,400 to Jena (14 per 1000), +1,400 to Eisenach (33 per 1000) and +1,300 to Weimar (21 per 1000). Between Thuringia and the other German states, the balance is negative: In 2012, Thuringia lost 6,500 persons to other federal states, the most to Bavaria, Saxony, Hesse and Berlin. Only with Saxony-Anhalt and Brandenburg the balance is positive. The international migration is fluctuating heavily. In 2009, the balance was +700, in 2010 +1,800, in 2011 +2,700 and in 2012 +4,800. The most important countries of origin of the