Fewer than five percent of Bulgaria\'s 7.36 million inhabitants declared themselves as Roma, final census data showed Thursday, while experts estimate the proportion is actually twice as high. \"Some 325,343 people or 4.9 percent of the population declared they belonged to the Roma ethnic group, or 0.2 percentage point more than in the previous census in 2001,\" the national statistical institute said in a statement. In the case of the ethnic Turks, their number totalled 588,318, equivalent to 8.8 percent of the overall population, a decline of 0.6 percentage point from 10 years ago. Some 5,664,624 people, or 84.8 percent of the population, described themselves as Bulgarian. The census was carried out in February and the question about ethnicity was optional, with 9.0 percent of people choosing not to answer it. But a minority expert, Mihail Ivanov, believed that as many as 390,000 Romas declared themselves to be Bulgarian, Turkish and even Romanian instead of Roma on the census questionnaire. \"In addition to those who listed themselves as Roma, there is another group of people of the same social characteristics that other people recognise as Roma,\" even if they did not list themselves as such, Ivanov told AFP. That would be in line with experts\' estimations that there are actually more than 700,000 Roma living in Bulgaria, equivalent to around 10 percent of the population. In linguistic terms, just 4.2 percent of Bulgarians listed Roma as their mother tongue, 9.1 percent Turkish and 85.2 percent Bulgarian, according to the census results. On the question of religion, which was also optional, 79.2 percent of Bulgarians gave a response, with 76 percent of those listing themselves as Christian Orthodox, 10 percent as Muslims and 0.8 percent as Roman Catholics or Protestants. The Bulgarian population has declined by 7.3 percent in the 10 years since the last census, but the ethno-religious structure has remained more or less intact, according to another expert Binka Denkova.