The best available estimate is that about ten million to twelve million Roma live in Europe, with large concentrations in Central and Eastern Europe. The majority of Roma live in extended families within segregated communities characterized by poverty, unemployment, poor education, and poor-quality housing. Roma communities are closely knit, characterized by limited social contact with non-Roma, while rules of behavior are culturally prescribed with distinct gender roles. Since coming to Europe, the Roma have been received with hostility and much of their history has been characterized by persecution by non-Roma. Despite their presence in the Balkans for centuries, integration of the Roma into their host societies is poor. During the communist era in Central and South-Eastern Europe, many Roma benefited from the system, whereas in the period of transition to capitalism the Roma have become the biggest losers. Currently, in the populations of the post-communist states, the Roma number between three and ten percent, and are the population group worst affected by unemployment in all countries. Thus, they have high levels of unemployment, substandard housing, lack of education and skills, and increasing dependence on state benefits and services. At the same time, their birth rate is more than twice the national average. In most countries, the Roma have remained a separated and distinctive ethnic group, retaining their group identity by not cooperating in one very important way: marriage.