Structural and macro reasons

・ Increasing growth of population during current decades and migration of rural labor force to cities especially large cities;

・ Lack of policies and coordinated strategies of economic, social and planning development at regional and macro level;

・ Intensified inequality within distribution of power, wealth and income sources and presence of regional inequalities;

・ Lack of socio-economic strategies in order to enabling participation of people to create appropriate conditions for immigrants;

・ Inefficiency of management system and planning of urban and regional development.

Non-structural and case reasons

・ Lack of appropriate development of educational system of professional and technical system in urban and rural areas and lack of appropriate places for training the required jobs in poor areas of cities;

・ Lack of programs of social and cultural development to enable people at personal and social levels within squatter areas in order to have economic and social self-reliance in new urban life;

・ Lack of culture in urban community to attract and emerge these groups in common urban contexts;

・ No pay attention to investment on low-price houses in poor and sub-urban areas of large cities;

・ Lack of comprehensive approaches, programs and policies in urban planning system and management;

・ Lack of appropriate policy for spontaneous organizations of people in poor urban areas and lack of support of urban management and organizations from formation of associations and non-governmental organizations and social institutions (under the supervision of Hossein Kakooee et al., 2003, introduction of scientific secretary);

・ Lack of access to formal systems of credits and mortgages for low-incom people especially those who work in informal sector;

・ Presence of illegitimate bands and land traders along with inability to supervise and control construction especially in spaces among cities;

・ Lack of institutes to aggregate the sources of low-income groups and lack of governmental supports from housing (Sarrafi, 2002, P. 7)

・ Some scholars consider this phenomenon because of urban and rural migration and sufficient supply of urban housing (Esmaeelpoor, 2010).