However, that population growth is not distributed evenly across all countries. Most population growth comes from developing countries, where birthrates remain high. Meanwhile, about half the world lives in nations with sub-replacement fertility. In some of these countries, the population has actually begun to shrink e.
All of the nations of East Asia — with the exceptions of Mongolia, the Philippines, and Laos — have fertility rates below replacement level. Russia and Eastern Europe are dramatically below replacement fertility. Western Europe also is below replacement. Some countries still have growing populations due to high rates of immigration, but have native fertility rates below replacement: Canada, Australia, and New Zealand are similar to Western Europe, while the United States is just barely below replacement with about 2.
A new fear for many governments, particularly those in countries with very low fertility rates, is that a declining population will lead to underpopulation and will reduce the gross domestic product GDP and economic growth of the country, as population growth is often a driving force of economic expansion.
To combat extremely low fertility rates, some of these governments have introduced pro-family policies that include incentives, such as payments to parents for having children and extensive parental leave for parents. Slums in Mumbai : Rapid population growth in Indian cities has resulted in vast slums as populations have exceeded available land and housing. The basics of demographic population growth depend on the rate of natural increase births versus deaths and net migration.
Demography is the statistical study of human populations. It can be a very general science that can be applied to any kind of dynamic living population, or one that changes over time or space. Human population growth depends on the rate of natural increase, or the fertility rate minus the mortality rate, and net migration. The basics of demography can be reduced to this formula:. As this equation shows, population change depends on three variables: 1 the natural increase changes seen in birth rates, 2 the natural decrease changes seen in death rates, and 3 the changes seen in migration.
Changes in population size can be predicted based on changes in fertility, mortality, and migration rates. Natural increase refers to the increase in population not due to migration, and it can be calculated with the fertility rate and the mortality rate.
Net migration is the mathematical difference between those migrating into a country and those migrating out of a country. This basic equation can be applied to populations and subpopulations.
For example, the population size of ethnic groups or nationalities within a given society or country is subject to the same sources of change as the national population. Individuals who change their ethnic self-labels or whose ethnic classification in government statistics changes over time may be thought of as migrating or moving from one population subcategory to another.
More generally, while the basic demographic equation holds true by definition, the recording and counting of events births, deaths, immigration, emigration and the enumeration of the total population size are subject to error. Allowance needs to be made for error in the underlying statistics when any accounting of population size or change is made. This means that population growth in the US is due to inward migration, rather than a high birthrate.
Population growth is difficult to predict because unforeseen events can alter birth rates, death rates, migration, or resource limitations. Explain the various ways sociologist try to estimate the rate of population growth, such as through fertility, birth and death rates. Forecasts try to estimate the rate of population growth, but this is understandably difficult to predict. For example, the UN has issued multiple projections of future world population, based on different assumptions.
From to , the UN consistently revised these projections downward, until the revision, issued on March 14, , revised the mid-range estimate upwards by million. The UN now estimates that, by , world population will reach 9 billion people. However, this forecast, like all population forecasts, is subject to change.
Population growth is difficult to predict because unforeseen events can alter birth rates, death rates, migration, or the resource limits on population growth. Countries may also choose to undertake mitigation measures to reduce population growth. For example, in China, the government has put policies in place that regulate the number of children allowed to each couple. Other societies have already begun to implement social marketing strategies in order to educate the public on overpopulation effects.
Certain government policies are making it easier and more socially acceptable to use contraception and abortion methods. Such policies could have a significant effect on global fertility rates. An estimated million women in the poorest countries of the world either did not want their last child, do not want another child or want to space their pregnancies, but they lack access to information, affordable means and services to determine the size and spacing of their families.
In the United States, in , almost half of pregnancies were unintended. At the same time, other countries may roll back access to contraception, as has happened recently in Afghanistan. In the period, Jews still are projected to have the highest life expectancy of all the major religious groups, a global average of 85 years, five years longer than at present.
But the greatest gains in longevity over the next four decades are expected among Hindus, whose global average life expectancy is projected to rise from 66 years in to 75 years in By , however, the median age of the population was 28 years. And by , the global median age is expected to be 37, as declining fertility rates lead to relative stability in the number of young children and as the elderly population soars. The United Nations estimates that the number of people ages and older will rise from about , in the year to more than 3 million in But as the global population ages, this distribution will shift, particularly among the youngest and oldest cohorts.
By , according to U. The youthfulness of a population is an important factor in future growth. All else being equal, a population that begins with a relatively large percentage of people who are in — or soon will enter — their prime childbearing years will grow faster than a population that begins with many people who are beyond their prime reproductive years. This reflects the geographic concentration of the unaffiliated in countries such as China and Japan, which have relatively old populations with low fertility rates.
By contrast, more than a quarter of Christians worldwide and three-in-ten Hindus were in the youngest age group as of This reflects the high fertility rates in recent decades among Christians in sub-Saharan Africa and Hindus in India. For the purposes of projecting future growth, the number of women in their early reproductive years also is a key factor.
In many countries, it is fairly common for adults to switch from identifying with the religion in which they grew up to identifying with another religion or with no religion. This collection of data provides the most comprehensive picture available to date of global patterns of switching among major religious groups, including from having been raised in a religion to being religiously unaffiliated as an adult.
Levels of switching are different for men and women. But at the global level, net movement due to the religious switching of men and women follows similar patterns. The chart below shows the projected total amount of movement into and out of major religious groups between and for countries with data on switching. The largest net movement is expected to be out of Christianity 66 million people , including the net departure of twice as many men 44 million as women 22 million.
Similarly, net gains among the unaffiliated 61 million are projected to be more than twice as large for men 43 million as for women 19 million. Muslims and followers of folk religions and other religions are expected to experience modest gains due to religious switching. Jews and Buddhists are expected to experience modest net losses through religious switching.
At the regional level, some patterns stand out. The largest projected net gains from switching between and are into the ranks of the unaffiliated, particularly in North America 26 million , Europe 24 million , Latin America 6 million and the Asia-Pacific region 4 million. But in sub-Saharan Africa, the greatest net gains are expected for Muslims 3 million. The largest net losses are expected among Christian populations, notably in North America 28 million , Europe 24 million , Latin America and the Caribbean 9 million and sub-Saharan Africa 3 million.
In the Asia-Pacific region, Christians are expected to have a net loss, due to religious switching, of more than 2 million adherents. Religious switching may have a large impact on the religious composition of individual countries. But over the year horizon of these projections, it is expected to have only a modest effect on the global size of most religious groups.
The global impact of religious switching can be seen by comparing the main projection scenario used in this study, which models switching in 70 countries, with two hypothetical scenarios — one in which switching is modeled in a total of a countries, and one that assumes no switching will occur anywhere. In the second scenario considered here, switching is projected in an additional 85 countries by using some of the initial 70 countries as proxies for switching patterns in similar, often neighboring, nations.
The third scenario assumes that no religious switching will take place from to , meaning that every adult will remain in the group in which he or she was raised. All those raised as Christians will stay Christian, all those raised without a religion will stay unaffiliated, and so on. The biggest differences in the outcome of these three scenarios are the size of the Christian and unaffiliated populations in It is slightly lower When switching is modeled in 70 countries — the main scenario — When switching is modeled for an additional 85 countries using proxy data, the projections show Comparing the outcomes of these three scenarios suggests that religious switching — at least at recently observed levels, in the limited number of countries for which data on switching are available — will have a relatively small impact on the projected size of major religious groups in Because of a lack of reliable data on religious switching in China, none of the scenarios models religious switching among its 1.
See sidebar on China at the end of this chapter. International migration has no immediate impact on the global size of religious groups. But, over time, migration can significantly change the religious makeup of individual countries and even entire regions. Europe, for example, has experienced an inflow of Muslims from North Africa, South Asia and Turkey over the past decade. Estimating future migration is challenging because the movement of people across borders is dependent on government policies and international events that can change quickly.
And because many migrants follow economic opportunities, migration patterns also are dependent on changing economic conditions. Nonetheless, it is possible to use data on past migration as a reasonable estimate for the future, just as past fertility and religious switching patterns are used in this report to model future fertility and switching. The Pew Research Center, in collaboration with researchers at the International Institute for Applied Systems Analysis, has developed an innovative technique to estimate recent migration patterns and their religious breakdown.
First, recent changes in the origins and destinations of migrants worldwide are estimated using census and survey data about the migrant population living in each country. Finally, the religious breakdown of migrant flows is used to calculate migration rates into and out of most countries by religion, by sex and by five-year age groups. For more detail on how future migration was projected, see the Methodology.
Between and , approximately 19 million people are expected to move across international borders. Muslim migrants, numbering about 6 million in total, are expected to come largely from the Asia-Pacific and Middle East-North Africa regions, migrating within those same regions as well as to Europe and North America. As a result of these movements from one region to another, the Asia-Pacific region is projected to experience a net loss of approximately 2 million Muslims and , Hindus between and The Latin America-Caribbean region is likely to see a net loss of 3 million Christians from migration.
And sub-Saharan Africa is projected to have a net loss of about , Christians and Muslims, combined. However, the birth rates in these regions are relatively high, and their current populations are relatively young.
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Explore This Subject. And all that consumption contributes to ecological degradation, increased conflicts, and a higher risk of large-scale disasters like pandemics. An increase in population will inevitably create pressures leading to more deforestation, decreased biodiversity, and spikes in pollution and emissions, which will exacerbate climate change. Ultimately, unless we take action to help minimize further population growth heading into the remainder of this century, many scientists believe the additional stress on the planet will lead to ecological disruption and collapse so severe it threatens the viability of life on Earth as we know it.
According to estimates in a study by Wynes and Nicholas , a family having one fewer child could reduce emissions by The scarcity brought about by environmental disruption and overpopulation has the potential to trigger an increase in violence and political unrest.
Many of the recent novel pathogens that have devastated humans around the world, including COVID, Zika virus, Ebola, and West Nile virus, originated in animals or insects before passing to humans. As we carry out our work at Population Media Center PMC , we see first-hand that spreading awareness about family planning methods and the ecological and economic benefits of having smaller families can change reproductive behavior.
Look Again! Discover how PMC is taking action against overpopulation today! All Rights Reserved. Privacy Policy. The Causes of Overpopulation Today the Earth is home to more than 7. Falling Mortality Rate The primary and perhaps most obvious cause of population growth is an imbalance between births and deaths.
Underutilized Contraception The global fertility rate has fallen steadily over the years, down from an average of 5 children per woman in to 2.
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