World Population Day | It's a numbers game

Asia is home to more than half the world's total population, with over 4.4 billion people and rising.

China, with about 1.38 billion people, is the most populous nation, but India is projected to take over that title in less than a decade.

Better healthcare and an increase in life expectancy are the main factors allowing the world population to grow about 1.13% per year, experts say.

(Ritchie B. Tongo / EPA)

Taipei, Taiwan:Early morning rush hour in Taipei. Asia's population is more than 4.4 billion people and rising, more than half of the world's total population.

(Harish Tyagi / EPA)

New Delhi, India: Potable water is distributed from a tanker truck in the Indian capital, whose estimated population of 17 million people puts tremendous pressure on basic services, like drinking water. (

(Francis R. Malasaig / EPA)

Manila: Filipino children rest among concrete culverts at a shantytown in Manila. The Philippines' popoulation is more than 102 million based on the latest United Nations estimates.

(Luong Thai Linh / EPA)

Hanoi, Vietnam: A nurse bathes a newborn baby at a hospital in Hanoi. Vietnam's population is estimated to reach 92.7 million in 2016, up 1.08% from 2015.

(Pablo Blazquez Dominguez / Getty Images)

Hong Kong:Two men sit in their "coffin homes," measuring 16 cubic feet each, in an illegally sub-divided apartment in Hong Kong. The mainly single male tenants pay $224 per month to rent a cubicle, with access to only two toilets for 22 tenants, and no kitchen or shower.

(Javier Lizon / EPA)

Beijing: Commuters line up at a bus station in Beijing. China is the most populous country in the world with 1.38 billion people, or 18.72% of the total world population, according to the latest United Nations estimates.

(Ander Gillenea / Getty Images)

Kathmandu, Nepal: An aerial view of the old Ason market in Kathmandu. The population of Nepal is estimated at 28.7 million.

(Daniel Ochoa de Olza / Associated Press)

Guwahati, India: A trash mountain at the garbage landfills site near Guwahati city in Assam, India.

(Miguel Riopa / AFP/Getty Images)

Loni, India: Passengers hang from an overcrowded train as it departs from Loni. India's population in 2016 is estimated at 1.33 billion.

(Pedro Armestre / AFP/Getty Images)

Tokyo: People ride down an escalator at a shopping mall in Tokyo, whose population was estimated at 13.5 million, up 2.7% since the 2010.