The effects of rapid urbanization on urban areas Urbanization is the growth in the proportion of people living in urban to rural areas and has occurred rapidly over the last 200 years, particularly between 1800 and 1800 1850, where a population explosion occurred. Furthermore, more recently, between 1950 and 1990, the percentage of people in the world living in urban areas increased by 20%. Currently, the rate of urbanization is much slower in MEDC countries than in LEDC countries as the vast majority of the population already lives in urban areas. The two main factors that influence urbanization are immigration and natural growth. First, the main reason for migration is "push and pull" factors, and these in this case are things that attract them to urban areas and things that push them away from rural areas. Secondly, natural growth affects urbanization because, in urban areas, there are overall more young people giving birth, and therefore a higher birth rate and a lower mortality rate, thanks to easy access to hospitals, medicines , etc. These two factors then increase the proportion of people living in urban areas, which means that urbanization has taken place. Urbanization has dramatic effects on countries, leaving behind advantages and disadvantages. Sao Paulo, Brazil is a classic example of an area where rapid urbanization has taken place. São Paulo is the third largest city in the world, with a population of 24 million, and is continually growing (sprawl). Urbanization has affected this city dramatically, causing several problems in living standards, housing, transportation and causing more and more unemployment. Due to the extreme natural growth rate and migration to São Paulo, the city cannot develop at a fast enough pace, resulting in a lack of housing. Due to the high demand for housing, house prices can rise, meaning poorer people are forced to build their own squatter settlements. About 8 million people in São Paulo live in these illegal settlements, or about 30% of the population..