Though still comparatively rural, Bangladesh has an urban population of about 35 million, or just over 25 percent of its total population. Moreover, the urban population has been growing very rapidly since liberation in 1971 and continues to do so at over 3.5 percent annually. The country will likely have an urban population approaching 50 million by 2015.This rapid growth has been due primarily to migration by the rural poor, particularly to large metropolitan areas. On arrival, these poor migrants routinely turn to slums and squatter settlements for shelter. All major urban centres in Bangladesh have slums and squatter settlements, the largest concentrations being in Dhaka, followed by Chittagong, Khulna, and Rajshahi. To begin with, there is no difference between a slum and a squatter settlement. The latter are simply slums illegally located on land belonging to the government, semi-governmental units, public organizations and other organizations. Drawing on both international literature attempting to define slums as well as widely accepted definitions or norms applied in the Bangladeshi context; slums are defined as settlements with a minimum of 10 households or a mess unit with a minimum of 25 members and:
* predominantly very poor housing;
* very high population density and room crowding;
* very poor environmental services, especially water and sanitation;
* very low socio-economic status;
* lack of security of tenure
The socioeconomic status of the community is defined by low income, with the majority, or over 50 percent, of households having income below the poverty level of Tk. 5,000 per month , the majority of the labour force in informal sector occupations (e.g. rickshaw pullers, hawkers, domestic workers, etc.) or very low paying formal sector positions (in organizations ranging from factories to offices) and low levels of rent. Another important dimension is whether the settlement is socially perceived as a slum. Finally, security of tenure is captured by vulnerability to eviction.