Measures to solve demographic problems. Business Club Magazine. Issue 11, 2017. pp. 18-20. (in Bulgarian and English) Ethnic groups The following table shows the ethnic composition of all Provinces of Bulgaria according to the 2011 census(% from the declared): Languages The 2001 census defines an ethnic group as a "community of people, related to each other by origin and language, and close to each other by mode of life and culture"; and one's mother tongue as "the language a person speaks best and usually uses for communication in the family (household)". According to the 2011 census, among the Bulgarians 99.4% indicate Bulgarian as a mother tongue, 0.3% - Turkish/Balkan gagauz, 0.1% - Roma and 0.1% others; among Turks 96.6% have pointed the Turkish/Balkan Gagauz as a mother tongue and 3.2% - Bulgarian; among the Roma 85% indicate Roma language as a mother tongue, 7.5% - Bulgarian, 6.7% - Turkish/Balkan gagauz and 0.6% - Romanian. Religion Bulgaria's traditional religion according to the constitution is the Orthodox Christianity, while Bulgaria is a secular state too. Since the last two censuses (2001 and 2011) provide widely divergent results, they are both shown in the table below. It is noteworthy that over a fifth of the population chose not to respond to this question in the 2011 census. {| style="border="0" |- | style="width:120px;"| | style="width:100px;"| | style="width:250px;"| |- | | 2001| 2011''' |- | Orthodox Christian | 82.6% | 59.4% |- | Muslim | 12.2% | 7.8% (7.4% Sunni; 0.4% Shia)|- | Catholic | 0.6% | 0.7% |- | Protestant | 0.5% | 0.9% |- | Other| 0.2% | 0.15% |- | None| 3.9% | 9.3% |- | No response| - | 21.8%'' |} The results of the Bulgarian 2011 Census, in which the indication of answer regarding the question for confession was optional, are as follows: The results of the Bulgarian 2001 Census by ethnic groups, the latest census in which the indication of identification (whether by confession or as irreligious) in the question for confession was obligatory, are as follows: Migration In relation to internal migration, according to the 1910 census, 300,000 or almost 10% of the ethnic Bulgarians were born in another Bulgarian municipality than the one they were enumerated in. The same data shows that the foreign-born ethnic Bulgarians numbered 78,000, or 2% of them, most numerous of whom were the 61,000 Ottoman-born, 9,000 Romanian-born and by less than 2,000