Total Population of the World by Decade, 1950-2050

How big will it get?

Population projections can vary drastically, even if they're working from the same population data. The UN Population Division projects that the world population will top out at around 11 billion, based on the average result of many different projections. 

Time will tell how the COVID pandemic of 2020 will affect these models. The far-reaching economic consequences of coronavirus will likely have some effect on growth rates, despite making a comparatively small impact on population sizes. 

Climate change is another variable that will have a drastic effect. Changes in the environment threaten important food production regions, like the Caribbean and the rainforests of Latin America (e.g. Brazil, which is the world's leading producer of soy and sugar cane). India, another major producer of global foods, is also at risk of instability due to climate change.

Demographic trends

Back in the 1960s and 1970s, when the population of the world reached its peak growth rate, there were many concerns about runaway population growth. Estimates of world population from recent years show that, while the total population is still growing, population growth has slowed considerably in the 21st century. The global fertility rate has dropped by nearly 50% from the 1950s. 

A large part of this reduction has been due to the drastic drop of fertility rates in developed countries, especially in Europe and Japan. Data suggest that as women get better access to birth control and are more able to participate in the workplace, the birth rate declines. Demographers also think that urbanization plays an important role in population change; children are more likely to work in agricultural societies, so there is more of an incentive to have more children. 

There are some data that suggest a certain level of development can loop back around and cause an increase in the total fertility rate. As life expectancies increase and healthcare improves, many women might elect to have children later in life. In the United States, a 2018 Pew Research poll found that number of people with kids was higher than in 1994. This was attributable to a big bump in women having children between 34 and 44. 

Most of the world's population increase is occurring in sub-Saharan Africa and southern Asia, especially in Nigeria and India. Their recent economic surges have 

The two exceptions to this are the United States and China, which both number among the fastest growing countries (and are two of the three most populous countries all ready). The United States has a fertility rate comparable to other developed countries, but it has a rate of immigration that keeps its population well above replacement levels. China would have likely been the fastest growing, if not for the ongoing effects of their (now abandoned) one-child policy. 

Source: Pew Research Center, U.S. Census Bureau, International Database, United Nations Population Division (World Population Prospects report)