Latest survey shows that 3 out of 4 people make up 75% of the world's population.

The United Nations Population Fund estimates that in one week, on October 31, 2011, the world's population will reach 7 billion. Just 200 years ago, there were only 1 billion people on the planet, and over the next 150 years, that number grew to 3 billion. But in the past 50 years, the global population has more than doubled, and the UN projects that it could possibly grow to 15 billion by the year 2100. As the international organization points out, this increasing rate of change brings with it enormous challenges. Meeting the basic needs of so many will meaning growing, shipping, and distributing more food while providing more clean water, health care, and shelter -- all without inflicting too much further damage on our environment. {Read the full article}

A densely populated neighborhood in West Delhi, India, seen from above via Google Earth.

Motorists crowd at a junction during rush hour in Taipei, on October 29, 2009. There are more than 8.8 million motorcycles and 4.8 million cars on Taiwan's roads and nearly all motor vehicles and inhabitants are squeezed into a third of the island's area. (Reuters/Nicky Loh)

A view of a residential building in Shanghai, China, on March 18, 2009. Shanghai is currently the most populous city in the most populous nation in the world, home to more than 23 million residents. (Reuters/Stringer)

People gather to get water from a huge well in the village of Natwarghad in the western Indian state of Gujarat on June 1, 2003. (Reuters/Amit Dave)