World Population Day is observed annually on 11 July to raise awareness of global population issues. The date was chosen because it was on or around 11 July 1987 that the world's population reached five billion people. That figure is now nearly 7.5 billion, and the United Nations estimates it will be around 11.2 billion by the year 2100. Part of the problem is that people are living longer – life expectancy at birth increased from 30 to 67 between 1800 and 2005.

China is the world's most populous country with around 1.4 billion inhabitants, but its population is falling, and India is catching up rapidly. This year's theme is "investing in teenage girls" who face a lack of school and early marriage and motherhood which leaves them vulnerable to illness, injury and exploitation.

The growth of the world's population affects sustainability, urbanisation, health, inequality, poverty and global warming. To mark World Population Day 2016, IBTimes UK presents this gallery of overcrowding and huge gatherings around the globe.