Geodemography is the study of people based on where they live.; it links the sciences of demography, the study of human population dynamics, and geography, the study of the locational and spatial variation of both physical and human phenomena on Earth, along with sociology. It includes the application of geodemographic classifications for business, social research and public policy but has a parallel history in academic research seeking to understand the processes by which settlements (notably, cities) evolve and neighborhoods are formed. Geodemographic systems estimate the most probable characteristics of people based on the pooled profile of all people living in a small area near a particular address. Origins The origins of geodemographics are often identified as Charles Booth and his studies of deprivation and poverty in early twentieth century London, and the Chicago School of sociology. Booth developed the idea of 'classifying neighborhoods', exemplified by his multivariate classification of the 1891 UK Census data to create a generalized social index of London's (then) registration districts. Research at the Chicago School – though generally qualitative in nature – strengthened the idea that such classifications could be meaningful by developing the idea of 'natural areas' within cities: conceived as geographical units with populations of broadly homogenous social-economic and cultural characteristics. The idea that census outputs could serve to identify and to characterize the geographies of cities gathered momentum with the increased availability of national census data and the computational ability to look for patterns in such data. Of particular importance to the emerging geodemographic industry was the development of clustering techniques to group statistically similar neighborhoods into classes on a 'like with like' basis. More recently, data have become available at finer geographical resolutions (such as postal units), often originating from private commercial (i.e. non-governmental) sources. Commercial geodemographics emerged from the late 1970s with the launch of PRIZM by Claritas in the US and Acorn by CACI in the UK. Geodemography has been used to target consumer services to 'ideal' populations based on their lifestyle and location. These parameters have been taken from geographical databases as well as from electoral lists and credit agencies. Combining these builds a picture of the population characteristics in different locations. The geodemographic data that this provides can then be used by marketers to target information towards those that they want to influence. This can be in the form of sales, services, or even political information. At