according to ali and toran, social networks might also explain rural–urban migration and people's ultimate settlement in slums. in addition to migration for jobs, a portion of people migrate to cities because of their connection with relatives or families. once their family support in urban areas is in slums, those rural migrants intend to live with them in slums urbanization a slum in rio de janeiro, brazil. rocinha favela is next to skyscrapers and wealthier parts of the city, a location that provides jobs and easy commute to those who live in the slums. the formation of slums is closely linked to urbanization. in 2008, more than 50% of the world's population lived in urban areas. in china, for example, it is estimated that the population living in urban areas will increase by 10% within a decade according to its current rates of urbanization. the un-habitat reports that 43% of urban population in developing countries and 78% of those in the least developed countries are slum dwellers. some scholars suggest that urbanization creates slums because local governments are unable to manage urbanization, and migrant workers without an affordable place to live in, dwell in slums. rapid urbanization drives economic growth and causes people to seek working and investment opportunities in urban areas. however, as evidenced by poor urban infrastructure and insufficient housing, the local governments sometimes are unable to manage this transition. this incapacity can be attributed to insufficient funds and inexperience to handle and organize problems brought by migration and urbanization. in some cases, local governments ignore the flux of immigrants during the process of urbanization. such examples can be found in many african countries. in the early 1950s, many african governments believed that slums would finally disappear with economic growth in urban areas. they neglected rapidly spreading slums due to increased rural-urban migration caused by urbanization. some governments, moreover, mapped the land where slums occupied as undeveloped land. another type of urbanization does not involve economic growth but economic stagnation or low growth, mainly contributing to slum growth in sub-saharan africa and parts of asia. this type of urbanization involves a high rate of unemployment, insufficient financial resources and inconsistent urban planning policy. in these areas, an increase of 1% in urban population will result in an increase of 1.84% in slum prevalence. urbanization might also force some people to live in slums when it influences land use by transforming agricultural land into urban areas and increases land value. during the process of urbanization, some agricultural land is used for additional urban activities. more investment will come into these areas, which increases the land value. before some land is completely urbanized, there is a period when the land can be used for neither urban activities nor agriculture. the income from the land will decline, which decreases the people's incomes in that area. the gap between people's low income and the high land price forces some people to look for and construct cheap informal settlements, which are known as slums in urban areas. the transformation of agricultural land also provides surplus labour, as peasants have to seek jobs in urban areas as rural-urban migrant workers. many slums are part of economies of agglomeration in which there is an emergence of economies of scale at the firm level, transport costs and the mobility of the industrial labour force. the increase in returns of scale will mean that the production of each good will take place in a single location. and even though an agglomerated economy benefits these cities by bringing in specialization and multiple competing suppliers, the conditions of slums continue to lag behind in terms of quality and adequate housing. alonso-villar argues that the existence of transport costs implies that the best locations for a firm will be those with easy access to markets, and the best locations for workers, those with easy access to goods. the concentration is the result of a self-reinforcing process of agglomeration. concentration is a common trend of the distribution of population. urban growth is dramatically intense in the less developed countries, where a large number of huge cities have started to appear; which means high poverty rates, crime, pollution and congestion. poor house planning lack of affordable low-cost housing and poor planning encourages the supply side of slums. the millennium development goals proposes that member nations should make a "significant improvement in the lives of at least 100 million slum dwellers" by 2020. if member nations succeed in achieving this goal, 90% of the world total slum dwellers may remain in the poorly housed settlements by 2020. choguill claims that the large number of slum dwellers indicates a deficiency of practical housing policy. whenever there is a significant gap in growing demand for housing and insufficient supply of affordable housing, this gap is typically met in part by slums. the economist has observed that "good housing is obviously better than a slum, but a slum is better than none". insufficient financial resources and lack of coordination in government bureaucracy are two main causes of poor house planning. financial deficiency in some governments may explain the lack of affordable public housing for the poor since any improvement of the tenant in slums and expansion of public housing programs involve a great increase in the government expenditure. the problem can also lie on the failure in coordination among different departments in charge of economic development, urban planning, and land allocation. in some cities, governments assume that the housing market will adjust the supply of housing with a change in demand. however, with little economic incentive, the housing market is more likely to develop middle-income housing rather than low-cost housing. the urban poor gradually become marginalized in the housing market where few houses are built to sell to them. colonialism and segregation an integrated slum dwelling and informal economy inside dharavi of mumbai. dharavi slum started in 1887 with industrial and segregationist policies of the british colonial era. the slum housing, tanneries, pottery and other economy established inside and around dharavi during the british rule of india. some of the slums in today's world are a product of urbanization brought by colonialism. for instance, the europeans arrived in kenya in the nineteenth century and created urban centers such as nairobi mainly to serve their financial interests. they regarded the africans as temporary migrants and needed them only for supply of labour. the housing policy aiming to accommodate these workers was not well enforced and the government built settlements in the form of single-occupancy bedspaces. due to the cost of time and money in their movement back and forth between rural and urban areas, their families gradually migrated to the urban centre. as they could not afford to buy houses, slums were thus formed. others were created because of segregation imposed by the colonialists. for example, dharavi slum of mumbai – now one of the largest slums in india, used to be a village referred to as koliwadas, and mumbai used to be referred as bombay. in 1887, the british colonial government expelled all tanneries, other noxious industry and poor natives who worked in the peninsular part of the city and colonial housing area, to what was back then the northern fringe of the city – a settlement now called dharavi. this settlement attracted no colonial supervision or investment in terms of road infrastructure, sanitation, public services or housing. the poor moved into dharavi, found work as servants in colonial offices and homes and in the foreign owned tanneries and other polluting industries near dharavi. to live, the poor built shanty towns within easy commute to work. by 1947, the year india became an independent nation of the commonwealth, dharavi had blossomed into bombay's largest slum. similarly, some of the slums of lagos, nigeria sprouted because of neglect and policies of the colonial era. during apartheid era of south africa, under the pretext of sanitation and plague epidemic prevention, racial and ethnic group segregation was pursued, people of colour were moved to the fringes of the city, policies that created soweto and other slums – officially called townships. large slums started at the fringes of segregation-conscious colonial city centers of latin america. marcuse suggests ghettoes in the united states, and elsewhere, have been created and maintained by the segregationist policies of the state and regionally dominant group. makoko – one of the oldest slums in nigeria, was originally a fishing village settlement, built on stilts on a lagoon. it developed into a slum and became home to about a hundred thousand people in lagos. in 2012, it was partially destroyed by the city government, amidst controversy, to accommodate infrastructure for the city's growing population. poor infrastructure, social exclusion and economic stagnation a large slum pictured behind skyscrapers in a more developed area in la paz, bolivia. social exclusion and poor infrastructure forces the poor to adapt to conditions beyond his or her control. poor families that cannot afford transportation, or those who simply lack any form of affordable public transportation, generally end up in squat settlements within walking distance or close enough to the place of their formal or informal employment. ben arimah cites this social exclusion and poor infrastructure as a cause for numerous slums in african cities. poor quality, unpaved streets encourage slums; a 1% increase in paved all-season roads, claims arimah, reduces slum incidence rate by about 0.35%. affordable public transport and economic infrastructure empowers poor people to move and consider housing options other than their current slums. a growing economy that creates jobs at rate faster than population growth, offers people opportunities and incentive to relocate from poor slum to more developed neighborhoods. economic stagnation, in contrast, creates uncertainties and risks for the poor, encouraging people to stay in the slums. economic stagnation in a nation with a growing population reduces per capita disposal income in urban and rural areas, increasing urban and rural poverty. rising rural poverty also encourages migration to urban areas. a poorly performing economy, in other words, increases poverty and rural-to-urban migration, thereby increasing slums. informal economy many slums grow because of growing informal economy which creates demand for workers. informal economy is that part of an economy that is neither registered as a business nor licensed, one that does not pay taxes and is not monitored by local or state or federal government. informal economy grows faster than formal economy when government laws and regulations are opaque and excessive, government bureaucracy is corrupt and abusive of entrepreneurs, labour laws are inflexible, or when law enforcement is poor. urban informal sector is between 20 and 60% of most developing economies' gdp; in kenya, 78 per cent of non-agricultural employment is in the informal sector making up 42 per cent of gdp. in many cities the informal sector accounts for as much as 60 per cent of employment of the urban population. for example, in benin, slum dwellers comprise 75 per cent of informal sector workers, while in burkina faso, the central african republic, chad and ethiopia, they make up 90 per cent of the informal labour force. slums thus create an informal alternate economic ecosystem, that demands low paid flexible workers, something impoverished residents of slums deliver. in other words, countries where starting, registering and running a formal business is difficult, tend to encourage informal businesses and slums. without a sustainable formal economy that raise incomes and create opportunities, squalid slums are likely to continue. a slum near ramos arizpe in mexico. the world bank and un habitat estimate, assuming no major economic reforms are undertaken, more than 80% of additional jobs in urban areas of developing world may be low-paying jobs in the informal sector. everything else remaining same, this explosive growth in the informal sector is likely to be accompanied by a rapid growth of slums. labour, work research in the latest years based on ethnographic studies, conducted since 2008 about slums, published initially in 2017, has found out the primary importance of labour as the main cause of emergence, rural-urban migration, consolidation and growth of informal settlements. it also showed that work has also a crucial role in the self-construction of houses, alleys and overall informal planning of slums, as well as constituting a central aspect by residents living in slums when their communities