Population Growth

Population Growth

Population Growth

Population growth is the change in a population over time, and can be quantified as the change in the number of individuals of any species in a population using "per unit time" for measurement. Population growth is used informally for the more specific term population growth rate, and is often used to refer specifically to the growth of the human population of the world. Simple models of population growth include the Malthusian Growth Model and the logistic model.

Determinants of Population growth

Population growth is determined by four factors, births, deaths, immigrants, and emigrants. The population growth of a period can be calculated in two parts, natural growth of population (Births-Deaths) and mechanical growth of population (Immigration-Emigration).

Population growth rate

Population growth rate is the fractional rate at which the number of individuals in a population increases. Specifically, it refers to the change in population over a unit time period, often expressed as a percentage of the number of individuals in the population at the beginning of that period. Natural increase is an increase in the native-born population, stemming from either a higher birth rate, a lower death rate, or a combination of the two. Net immigration rate is the difference between the number of immigrants and the number of emigrants. The most common way to express population growth is as a ratio, not as a rate. The change in population over a unit time period is expressed as a percentage of the population at the beginning of the time period. That is:

A positive growth ratio indicates that the population is increasing, while a negative growth ratio indicates the population is decreasing. A growth ratio of zero indicates that there were the same number of people at the two times -- net difference between births, deaths and migration is zero. However, a growth rate may be zero even when there are significant changes in the birth rates, death rates, immigration rates, and age distribution between the two times.

A related measure is the net reproduction rate. In the absence of migration, a net reproduction rate of more than one indicates that the population of women is increasing, while a net reproduction rate less than one (sub-replacement fertility) indicates that the population of women is decreasing.

Excessive growth and decline

Population exceeding the carrying capacity of an area or environment is called overpopulation. It may be caused by growth in population or by reduction in capacity. Spikes in human population can cause problems such as pollution and traffic congestion, these might be resolved or worsened by technological and economic changes. Conversely, such areas may be considered "underpopulated" if the population is not large enough to maintain an economic system (see population decline). Between these two extremes sits the notion of the optimum population.

Global population growth rate

Globally, the growth rate of the human population has been declining since peaking in 1962 and 1963 at 2.20% per annum. In 2009, the estimated annual growth rate was 1.1%. The CIA World Factbook gives the world annual birthrate, mortality rate, and growth rate as 1.915%, 0.812%, and 1.092% respectively. The last one hundred years have seen a rapid increase in population due to medical advances and massive increase in agricultural productivity.

The actual annual growth in the number of humans fell from its peak of 88.0 million in 1989, to a low of 73.9 million in 2003, after which it rose again to 75.2 million in 2006. Since then, annual growth has declined. In 2009, the human population increased by 74.6 million, which is projected to fall steadily to about 41 million per annum in 2050, at which time the population will have increased to about 9.2 billion. Each region of the globe has seen great reductions in growth rate in recent decades, though growth rates remain above 2% in some countries of the Middle East and Sub-Saharan Africa, and also in South Asia, Southeast Asia, and Latin America.

Some countries experience negative population growth, especially in Eastern Europe mainly due to low fertility rates, high death rates and emigration. In Southern Africa, growth is slowing due to the high number of HIV-related deaths. Some Western Europe countries might also encounter negative population growth. Japan's population began decreasing in 2005.

Australian Population Growth Rate

The rate of population growth changed significantly following the Australian gold rushes, the Great depression and World War II. At the time of Australian Federation in 1901, the rate of natural increase was 14.9 persons per 1,000 population. The rate increased to a peak of 17.4 per thousand population in the years 1912, 1913 and 1914. During the Great Depression, the rate declined to a low of 7.1 per thousand population in 1934 and 1935. Immediately after World War II the rate increased sharply as a result of the beginning of the post–World War II baby boom and the immigration of many young people who then had children in Australia, with a plateau of rates of over 13.0 persons per 1,000 population for every year from 1946 to 1962.

There has been a fall in the rate of natural increase since 1962 due to falling fertility. In 1971 the rate of natural increase was 12.7 persons per 1,000 population; a decade later it had fallen to 8.5. In 1996 the rate of natural increase fell below seven for the first time, with the downward trend continuing in the late 1990s. Population projections by the Australian Bureau of Statistics indicate that continued low fertility, combined with the increase in deaths from an ageing population, will result in natural increase falling below zero sometime in the mid 2030s. However in 2006 the fertility rate rose to 1.81, one of the highest rate in the OECD, arguably as a result of some pro-fertility state and federal government campaigns, including the Federal Government's baby bonus. Since 1901, the crude death rate has fallen from about 12.2 deaths per 1,000 population to 6.4 deaths per 1,000 population in 2006.

FURTHER READING
Australian Population Growth and Migration
3218.0 Regional Population Growth Australia
ABS 3101.0 Australian Demographic Statistics
Population Demographic Discussion
Australia Population Growth Graph
Australian City Population
Australian Population 2050
Australian Population Density
Australian Population Distribution
Australian Population History
Australian Regional Population Growth
Human Population Growth
Meaning Population Growth
Population City
Population Definition
Population Density
Population Growth
Population Growth and Distribution Australia
Population Growth Formula
Population Growth Rate
Population Growth Statistics
Population of Australia
Population of Aus
Population of Countries
Population Statistics
World Population
World Population Clock
World Population Growth
Zero Population Growth