The world population has already increased from 2.5 billion in 1950 to 7.3 billion in 2015. It will further grow to 9.7 billion in 2050 and 11.2 billion in 2100 (median of probabilistic projections).

World population increase has peaked in the five-year period between 1985 and 1990, when 457 million were added to the world population. However, increases in world population have not declined much since then. Between 2010 and 2015, the world population grew by some 420 million people - not much less than in the late 1980s.

The number of people added to the world population in each subsequent five-year period is projected to decline - but only after 2050 will the numbers added to the world population be smaller than in the early 1950s.

Currently, Africa is adding rapidly increasing numbers of people to its population: Between 2010 and 2015 Africa's population grew by some 142 million. In the future, Africa's population increase will be up to 213 million, which will be added in the five-year period between 2055 and 2060.

Africa has experienced, and will further see, explosive population growth. The continent's population will increase from some 229 million in the early 1950s to more than 4.4 billion people by the end of the 21st century (according to the median of probabilistic population projections).

With a 95 per cent degree of confidence the global population will be between 9.3 and 10.2 billion in 2050 and between 9.5 and 13.3 billion in 2100.

In 1950, Africa had only some 229 million inhabitants. Today, the population is already 1.2 billion und it is quite likely that it will double over the next 35 years and reach 2.4 billion by 2050 - despite the projected fertility decline.
By the end of the century, Africa's population could be 4.4 billion. In that case the continent will have added roughly 4.16 billion people to its 1950 population - all within a 150-year period.

Asia is now on its way to population stabilization or even decline - eventually approaching a more sustainable population size.

Over the next 35 years Europe's population (including Russia) will shrink to 707 million - primarily due to a rapid population decline in Eastern and Southern Europe. By the end of the 21st century, Europe's population could be down to 646 million.

Latin America and the Caribbean had a population of around 169 million in 1950. Since then it has quadrupled to about 634 million. However, population growth will soon begin to level off; after 2060 the population will probably decline.

Based on the probabilistic population projections of the United Nations Population Division one can say with a 95 percent degree of confidence that the population of Northern America will be between 409 million and 604 million by the end of the 21st century.

Africa's population was only half that of Europe by the middle of the 20th century. By now, the relation has reversed. While Europe's population increased by just 189 million over the past 65 years, Africa's population more than quintupled and has now reached 1.19 billion. By the end of the 21st century Africa's population could be almost 7 times the population of Europe.

The population of Latin America and the Caribbean will peak around 2060 and then begin to decline to about 721 million by the end of the 21st century. In Northern America the population is likely to increase beyond the end of the 21st century. By 2100 it might reach half a billion people.

In 1950, Asia's population was more than six times larger than Africa's. Today, it is less than four times larger and by the end of the 21st century Africa's population could be very close to that of Asia.

The 150-year period between the middle of the 20th century and the end of the 21st century will see an unprecedented increase in the human population.

It can be expected, that the world population will increase by almost 8.69 billion people between 1950 and 2100.

More than 88% of this increase will be in Africa (47.9%) and Asia (40.2%). Latin America and the Caribbean will only contribute some 6.4% to this world population increase and Northern America just 3.8%

Europe and Oceania will contribute just 1.1% and 0.7% to the world population increase between 1950 and the end of the 21st century.

The enormous increase of the world population from 2.5 billion in 1950 to most likely 11.2 by the end of the 21st century will essentially happen in Africa and Asia.

Rapid population growth of more than 2 or 3 percent per year, which is quite typical for many countries in Africa, causes major challenges for development. Such rates make it just difficult to feed, educate and train the population, provide health care, infrastructure and jobs. However, such growth rate also create opportunities.

A population decline can be caused by one or more of the following factors:
(1) A drastic fertility decline to the sub-replacement level.
(2) An increase of mortality - such as during war or natural disaster.
(3) A negative overall migration balance, and
(4) a significant net-emmigration of young people (even when overall migration is balanced). The loss of young people is causing population aging and leads to a shrinking in the number of potential parents, which will cause a decline in the number of births und thus population decline (even with constant fertility).
The consequences of population decline depend on the particular social, economic and political system. In densely populated countries population decline may be an advantage, because it reduces the burden on the environement. Population decline in sparsely populated countries, such as in many parts of Eastern Europe, can lead to population collapse and economic decline. Mostly affected by population decline are existing infrastructure and services that become under-utilized and therefore costly. Population decline can also threaten public finances, as well as pension and social security systems - in particular when combined with population aging. (See diagram for details.)

Since the middle of the 20th century it was primarily Asia that contributed to world population growth: From 1950 to 2015, Asia's population grew by almost 3 billion people; and it will most likely increase by another 874 million over the next 35 years. Africa's population has contributed 957 million to world population growth since 1950. However, over the next 35 years Africa's population will most likely contribute about 1.3 billion people.

(1) Over the past 65 years India and China saw the highest population increase by far. India alone added some 935 million people to the world population between 1950 and 2015. During the same period China contributed some 832 million people. This is far larger than the population increase in any other country of the world.

(2) Over the coming 35 years it is quite likely that India's population will grow by another 394 million - in stark contrast to China, where the population will actually decline by some 28 million between now and 2050. The country with the second largest population increase will be Nigeria, with an additional 216 million between today and 2050.

(3) In the second half of the 21st century, when predictions are, of course, more uncertain, Nigeria will be, by far, the country with the highest population increase: Nigeria could add some 354 million people to the world population between 2050 and 2100. The countries with the second and third biggest population increase will also be in Africa: the Democratic Republic of the Congo and the United Republic of Tanzania, which will increase their population by 193 and 162 million, respectively.

(4) In the 150-year period between 1950 and 2100, India will be the country that will add, by far, the largest number of people to the world population: 1.28 billion. Nigeria could add 714 million; but China "just" 460 million.

In 1950, the Democratic Republic of the Congo, the United Republic of Tanzania and Belarus had a population of around 8 million.
By the end of the 21st century the DR Congo might have a population of 389 million and Tanzania of 299 million. The population of Belarus will probably have declined to 7 million.

Ethiopia, Egypt and Poland had roughly the same population size in 1950: Between 18 and 25 million.

By 2100, Ethiopia's population could be around 243 million and Egypt's population could be some 201 million. However, the population of Poland will probably decline to 22 million.

In 1950, Nigeria, Pakistan and the Ukraine each had a population of around 37.5 million. By today, Nigeria's and Pakistan's population have already nearly quintupled to 182 million and 189 million, respectively.

However, population growth in Nigeria and Pakistan is far from over. Nigeria's population will most likely increase to around 399 million over the next 35 years. By the end of the century, Nigeria could have a population of more than 750 million.

Pakistan's population growth will be somewhat more moderate in the future: By 2050, Pakistan will probably have a population of around 310 million; by 2100, the population could be around 364 million - significantly less than in Nigeria.

By contrast, Ukraine's population which increased moderately from 37 million in 1950 to 45 million in 2015, is projected to decline to a little more than 26 million by the end of the 21st century.

In 1950, Niger, Iraq and Bulgaria had a population of 2.5 million, 5.7 million and 7.3 million, respectively. Today, Niger's population is slightly less than 20 million and Iraq's population is around 36 million. The population of Bulgaria is now less than 7.2 million.

Over the next 35 years, Bulgaria's population will probably decline to 5.2 million. Iraq's population could more than double to almost 84 million - despite the political and military crises. Niger's population, however, will most likely far more than triple to 72 million people in 2050. This increase is mostly the consequence of a very "young" population, which will generate large numbers of births - despite a rapid decline in fertility.

In the second half of the 21st century Niger's population could virtually "explode" and increase from 72 million in 2050 to 209 million in 2100. Iraq's population will "only" reach about 164 million by the end of the century.

Bulgaria's population, however, might easily decline to just 3.4 million people. If that happens, the country will have experienced a real population collapse in which the population will be less than half of its peak in 1985, when Bulgaria had a 9 million population.

This figure might be particularly relevant from a geo-strategic perspective. It illustrates the rising demographic weight of the United States of America - as compared to Western Europe and the Russian Federation.
The United States' population is increasing continuously - from around 158 million in 1950 to some 322 million today and to most likely around 450 million by the end of the 21st century.
Western Europe increased its population from 142 million in 1950 to about 191 million today. However, the region's population growth will level off and by 2100 the population might be slightly smaller than today.

Between 1950 and 2015, the Russian Federation, which until 1991 was the core region of the former Soviet Union, also increased its population: from around 103 million to about 150 million shortly before the dissolution of the Soviet Union. Since then it has declined to about 143 million. By the end of the 21st century, the population of the Russian Federation could decline to 117 million.

In geo-politics, population size matters - as is exemplified by the rise of China and India. Populous nations can not only supply manpower for very large armies; they can also project the economic power of large labor and consumer markets, if they have a functioning economy. The Russian Federation is seriously handicapped by its demographic decline, while the United States is accumulating an increasing human resource base.

By the end of the 21st century the United States of America will probably still "play" in the same league as China and India, while the Russian Federation will have fallen back to a medium-sized power. The size of Russia's consumer market, labor force and human talent base will be more in the range of those in Western Europe.