Population has been described as all the organisms that both belong to the same group or species and live in the same geographical area and by nature follows a pattern of change-from simplicity to complexity (Early Evolutionary Theory). Human population exhibits a J-shaped growth curve, and is accelerating. The world's population is 7 billion and the Earth's land area of 150 million km2 (58 million sq. miles), then human population density is 45.3 per km2 (117.2 per sq. mile). This calculation includes all continental and island area. If Antarctica is excluded, then population density rises to 50 people per km2 (129.28 per sq. mile
According to United States Census Bureau, the resident population of the United States, projected to 05/11/12 at 3:13 UTC (EST+5) is 313,521,703. The U.S. population clock shows a series of short-term projections for the resident population of the United States.
According to U.S. Census Bureau, there is a net gain of one person (including the component setting of one birth/ 8 seconds, a death for every 13 seconds and a migrant for 46 seconds) in USA for every 14 seconds. So the whole year of 2012 using the net gain has an estimation of 333,674,503 people in USA and for each year, there is an expected of 2,254,114 people to be added in the population of USA. The graph below shows the growth of the population from 2012-2192. It shows that after 150 years (2162), the population of USA will double and after 180 years (2192), the population will increase by 400 million.
According to the USCB, the world’s current growth rate is about 1.3 % (0.013). The latest projections imply that the population is projected to grow 6 billion (1999) to 9 billion (2044), an increase of 50 % that is expected to require for 45 years. Check the graph.
Before 2100, world’s population will double but “Sometime before 2100, the great centuries-long expansion of the world's population will have come to an end."
(Lutz, Sderson, and Scherbov, 2004)
One of the Philippine cities, Cebu City, is a densely populated city. The city faces lots of problem in housing and food allocation. Due to urbanization, many rural people go to the city and settle there. The influx caused the illegal settling and squatting that hinders the government to use and develop the lands for commercial and high standard residential sites. Since there are lots of squatters who don’t have high-earning jobs they find foods from the trash or by begging. Squatter areas also serve as the cause of the city’s pollution.