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
Optimum population Optimum population Optimum population refers to the size of a population that produces the best results according to chosen end targets. One text from 1926 presented a single end target as being "...the largest per capita income of consumers' goods possible under the given conditions". Other potential end targets in favour of lower levels of population are cited, including: long term sustainability, efficient operation of democracy, the preservation of personal freedom and the preservation of biodiversity while potential end targets in favour of higher levels of population are cited, including the abilities to preserve and foster cultural diversity, to stimulate