Human population has just reached the 8 billion mark on November 15th, 2022. This massive population is scattered across every corner of the globe, with concentrations in India, China, and the United States. With a population growth rate of .83%, the world population is expected to reach 9 billion in only 15 more years. Populations are expected to peak around 10.4 billion in 2080, according to UN projections. 

There are a lot of factors that lead to population growth. Life expectancy rates are one of the greatest indicators; since 1800, global life expectancy has increased from 29 to 73 years. Better global health and aging populations means that people are able to reproduce at an older age and be expected to live longer. Some countries, such as Nigeria and Pakistan, also have very high fertility rates that are growing the population significantly in those countries. There is an inverse relationship between the life expectancy of a country and its fertility rate.