I = PAT that human population may stabilize at around 11.2 billion in 2100, the I=PAT equation will continue to be relevant for the increasing human impact on the environment in the short to mid-term future. Increased population increases humans' environmental impact in many ways, which include but are not limited to: The variable A, in the I=PAT equation stands for affluence. It represents the average consumption of each person in the population. As the consumption of each person increases, the total environmental impact increases as well. A common proxy for measuring consumption is through GDP per capita. While GDP per capita measures
World population Health Organization, the global average life expectancy is 71.4 years as of 2015, with women living an average of 74 years and men approximately 69 years. In 2010, the global fertility rate was estimated at 2.52 children per woman. In June 2012, British researchers calculated the total weight of Earth's human population as approximately 287 million tonnes, with the average person weighing around . The CIA estimated nominal 2013 gross world product at US$74.31 trillion, giving an annual global per capita figure of around US$10,500. Around 1.29 billion people (18.4% of the world population) live in extreme poverty, subsisting on