Personal space is highly variable. Those who live in a densely populated environment tend to have smaller personal space requirements. Thus a resident of India may have a smaller personal space than someone who is home on the Mongolian steppe, both in regard to home and individual.
It can be determined on a habitat level by profession, livelihood, and occupation. Personal space can also be heavily affected by a person's position in society, with the more affluent a person being the larger personal space they demand. See also ethnic stereotype. While it is highly variable and difficult to measure accurately the best estimates for personal physical space place it at about 24.5 inches (60 centimeters) on either side, 27.5 inches (70 centimeters) in front and 15.75 inches (40 centimeters) behind for an average westerner.
In certain circumstances people can accept having their personal space violated. For instance in romantic encounters the stress from allowing closer personal space distances can be reinterpreted into emotional fervour. Another method of dealing with violated personal space, according to psychologist Robert Sommer, is dehumanization. He argues that, for instance on the subway, crowded people imagine those infiltrating their personal space as inanimate.
Attitudes of people regarding someone else entering their personal space may depend on the sex of both people. Some train cars are women-only, to allow women to avoid men entering their personal space, providing privacy, and safety from the possibility of being groped. Changing perceptions about personal space and the fluctuating boundaries of public and private in European culture since the Roman Empire have been explored in A History of Private Life, under the general editorship of Philippe Ariès and Georges Duby, published in English by the Belknap Press.