Geographical segregation exists whenever the proportions of population rates of two or more populations are not homogenous throughout a defined space. Populations can be considered any plant or animal species, human genders, followers of a certain religion, people of different nationalities, ethnic groups, etc. In social geography segregation of ethnic groups, social classes and genders is often measured by the calculation of indices such as the index of dissimilarity. Different dimensions of segregation (or its contrary) are recognised: exposure, evenness, clustering, concentration, centralisation, etc. More recent studies also highlight new local indices of segregation. Geographical segregation is most often measured with individuals' place of residence, but increasing geographical data availability makes it now possible to compute segregation indexes using individuals' activity space, in whole or in part. Human geographical segregation Segregation, as a broad concept, has appeared in all parts of the world where people exist—in different contexts and times it takes on different forms, shaped by the physical and human environments. The spatial concentration of population groups is not a new phenomenon. Since societies began to form there have been segregated inhabitants. Either segregated purposefully by force, or gradually over time, segregation was based on socio-economic, religious, educational, linguistic or ethnic grounds. Some groups choose to be segregated to strengthen social identity. Types Legal segregation Segregation can be caused by legal frameworks, such as in the extreme example of apartheid in South Africa, and even Jewish ghettoization in Germany in the 20th century. Segregation can also happen slowly, stimulated by increased land and housing prices in certain neighborhoods, resulting in segregation of rich and poor in many urban cities. Segregation can also be assigned arbitrarily. This can occur on a global scale, such as is seen in the Partition of India, instances in Ireland, and many other situations. Geographical boundaries were often put in place without much consideration for native peoples and natural geographic terrain and cultural limits that had long been in place. In apartheid South Africa, segregation was very much a legal concept. Enforced by the government, black and coloured South-Africans were discriminated against, and forced to comply with apartheid. Some of the legislation passed dealt with physical segregation in schools, land tenure, geographic segregation and state repression. These were very clearly legislative, but also in the case of most white South Africans, a social construct as well. Segregation can also be encouraged, using geographical boundaries, while