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
Smeed's law to speed traffic would only lead to more people driving at this "tolerable" speed unless there were any other disincentives against doing so. His hypothesis in relation to road traffic safety has been disputed by several authors, who point out that fatalities per person have decreased, when the "Law" requires that they should increase as long as the number of vehicles per person continues to rise. Smeed's formula is expressed as: or, weighted per capita, where "D" is annual road deaths, "n" is number of registered vehicles, and "p" is population. Smeed published his research for twenty different countries, and,