Estimated Population Size

Written by Thomas Godwin
Updated: May 1, 2023
Image Credit © blvdone/


The estimated population size, according to the World Population Clock, hit 8 billion on November 15, 2022. On any given day, birth rates double that of death rates, although that’s a worldwide average, and different countries generate different results.

Estimated Population Growth

The United Nations keeps records of population growth throughout the decades. Since 1950, the worldwide population has tripled, reaching the 8 billion point only a few months ago. The United Nations also estimates that the world population will increase to 9 billion by the year 2037.

The two most populous nations are China and India. Those two countries, compared to every other country on earth, are miles ahead in population terms. China’s population is currently 1.4 billion, mirrored by India at 1.4 billion.

Thousands of Hindu Pilgrims/ People in the holy city of Haridwar in Uttarakhand, India during the evening light ceremony called Ganga arthi to worship river Ganga / Ganges. Culture, Tradition,ceremony
The population of India is 1.4 billion people — the same as China.

©Vivek BR/

The United Nations also estimates that the worldwide population will reach 10.4 billion by the year 2100. That’s a population growth rate of 31,168,831 per year for the next 77 years.

Factors That Affect Estimated Population Size

Many factors affect estimated population size, including migration, societal stability, education, standards of health care, cultural attitudes towards family, contraception availability, economic growth, and societal norms.

Many of these are obvious factors that make sense in terms of population size and growth. However, some are more indirect in how they affect the population.

Estimated Population Size – Animals

Three methods are used to determine an estimated population size for any species of animal. It’s always about estimation. Trying to determine an accurate, precise number is all but impossible and requires far too many resources and time to pull off.

Random Sampling

To reach an estimated population through random sampling, some biologists use the random sampling technique. This technique is fairly simple and involves counting a few animals within a small area. The animals are counted and the biologist creates an estimate of a much larger area, wholly based on the limited sample in the smaller area.

Herd of Alpacas Grazing in Peru, near Cusco in the Andes Mountains
Animal population sizes are always estimates.


Mark, Release, and Recapture

This is the most common method for estimating the population of a specific species of animal. Biologists and Wildlife Rehabilitators capture and tag the animal in some way, whether it’s a simplistic tagging system or a sophisticated GPS tracking tag.

Biologists continue to do this for a specified amount of time. Afterward, the wait begins. After another specified amount of time, biologists begin capturing animals again. The estimated population is based on the ratio of untagged animals caught versus tagged. This is also known as the Lincoln Index.

Ground and Aerial Surveillance

This method is as simple as it sounds. Biologists target and observe specific animals, within the freedom of their natural habitats, by air and ground surveillance. Population estimates are tabulated according to the data gathered during the surveillance periods.

Factors That Affect Estimated Population Size of Animals

As with humans, many factors affect animal populations, including predation, competition, habitat, niche, availability of light, weather, urbanization, deforestation, and nutrition to name a few. There is an ongoing controversy about hunting and how it affects animal populations.

While overhunting, unregulated hunting, and trophy hunting negatively impact population sizes, regulated hunting helps to thin populations before the impact of winter, along with reducing competition over local resources, such as food and bedding.

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About the Author

Thomas is a freelance writer with an affinity for the great outdoors and Doberman Pinschers. When he's not sitting behind the computer, pounding out stories on black bears and reindeer, he's spending time with his family, two Dobermans (Ares and Athena), and a Ragdoll cat named Heimdal. He also tends his Appleyard Ducks and a variety of overly curious and occasionally vexatious chickens.