In the long run, future global population growth is difficult to predict. Population size fluctuates at differing rates in differing regions. Nonetheless, population growth is the long-standing trend on all inhabited continents, as well as in most individual states. In some countries, there is negative population growth (i.e. net decrease in population over time), especially in Central and Eastern Europe – this is mainly due to low fertility rates. During the 2010s, Japan and some countries in Western Europe are also expected to encounter negative population growth, due to sub-replacement fertility rates.

Interesting facts:

1. As of 2012, the global sex ratio is approximately 1.01 males to 1 female – the greater number of men is possibly due to the significant gender imbalances evident in the Indian and Chinese populations. Approximately 26.3% of the global population is aged under 15, while 65.9% is aged 15–64 and 7.9% is aged 65 or over. The global average life expectancy is 67.07 years, with women living an average of 69 years and men approximately 65 years. 83% of the world's over-15s are considered literate. In June 2012, British researchers calculated the total weight of Earth's human population as 287 million tonnes, with the average person weighing 62 kilograms (140 lb).
2. The Han Chinese are the world's largest single ethnic group, constituting over 19% of the global population, while the second-largest single ethnicity, the Bengali people, account for around 4.8%. The world's most-spoken first languages are Mandarin Chinese (spoken by 12.44% of the world's population), Spanish (4.85%), English (4.83%), Arabic (3.25%) and Hindi-Urdu (2.68%). The world's largest religion is Christianity, whose adherents account for 33.35% of the global population; Islam is the second-largest religion, accounting for 22.43%, and Hinduism the third, accounting for 13.78%. In 2005, around 16% of the global population were reported to be non-religious.