The Dictionary of Human Geography (21 page)

caste
An endogamous social hierarchy of enduring political significance, believed to have emerged some 3500 years ago around highly questionable categories of Aryans and non Aryans in the Indian subcontinent. The former comprising brahman, kshatriya and vaishya emerged as dominant occupational castes of so called dvija (twice born). The shudra caste(s) regarded as non Aryan and ?mixed' were occupationally marginalized and racialized, as was also the case later with the ?outcastes' (Dalit), whose touch was deemed polluting (Thapar, 1966). This order was challenged from the sixth century bce, but all major religions in India came to bear the social imprint of caste. Brahman social dominance was bolstered by a British neo Brahmanical ruling ideoLogy, and provoked a backlash (Bose and Jalal, 1997). Significantly, leaders such as Lohia analytic ally separated the high castes from women, shudra, Dalit, Muslim and adivasi (?indigen ous') and underscored the political necessity of marriages between shudra and dvija, while disrupting the rift between manual and brain work, which contributed to the formation, rigidification and violence of caste. rn (NEW PARAGRAPH) Suggested reading (NEW PARAGRAPH) Lohia (1964). (NEW PARAGRAPH)
catastrophe theory
Abranch of?bifurcation theory?, which is itself a branch of non linear dynamic systems theory. Bifurcation theory studies how, in certain non linear systems, there may be paths and shifts in behaviour dependent on small changes in circumstances or the current position of the system. One type is the sudden jump or catastrophe, where a dramatic change results from a small change in the parameters. Other forms of bifurcation include ?hysteresis?, where the reverse path to some point is not the same as the original path, and ?divergence?, where a small change leads the system towards a very different state (but not in a ?jump?). (NEW PARAGRAPH) Bifurcation and catastrophe theory were developed by the French mathematician Rene Thom in the early 1970s (Thom, 1975). In human geography, several studies suggested that it could be used to understand settlement pattern changes, both in terms of the sudden emergence and growth of cities and the sudden collapse of layers in a central place system (for a review of these and other studies, see Wilson, 1981). The difficulty with these, and with many other suggested applica tions in the social sciences, is that they were speculative and one had to assume particular non linear relationships and parameters to generate a system subject to catastrophes, and the perspective has not been as productive as many originally hoped. The most detailed and analytical developments in human geog raphy have been those by Wilson, which add dynamics in the classic retail, gravity and urban structure models and explore potential bifurcations. Like its relative chaos theory, catastrophe theory is now treated as part of the wider compLexity theory. Lwh (NEW PARAGRAPH) Suggested reading (NEW PARAGRAPH) Wilson (1981). (NEW PARAGRAPH)
categorical data analysis
A family of quan titative methods in which the variables are gauged at a low scale of measurement. Such variables may be binary categories (male/ female; rich/poor), ordered multiple categories (as in a Likert scale such as, unhappy, neutral, happy), unordered multiple categories (travel to work by car, foot, train, cycle), or a count (the number of crimes in an area). Such data often arise through survey anaLysis in which answers to questions are limited to a number of categories. Until the 1970s, analysis of such data was limited to simple description in a cross tabulation, testing for independence of variables through such procedures as chi square, and assessing association with a range of measures of correLation such as Cramer?s V and Yule?s Q. More recently, a full scale modelling approach has been developed for such data in a regression like framework. (NEW PARAGRAPH) All regression models consist of three com ponents: the response or outcome variable; a function of the predictor or explanatory vari ables; and a random term that represents the stochastic variation in the outcome variable that is not accounted for by the predictors. In a standard regression model the response is a continuous variable that is related to the pre dictors in a linear (straight line) fashion (the so called ?identity link?). With such a continu ous outcome, the random term is usually assumed to follow a normal distribution and is summarized by an estimate of the unex plained variation, such as the variance. In cat egorical data analysis, in what are known as generaLized Linear modeLs, the response is not continuous but discrete, the link between outcome and predictors is non linear, and the random distribution is not normal but takes an appropriate distribution, depending on the scale of measurement of the dependent variable. (NEW PARAGRAPH) A number of key members of the family are defined by different types of measurement for the response variable. One that is binary or a proportion with a relatively small absolute denominator (e.g. the unemployment rate for small areas) requires a logit link and a bino mial distribution; this is known as the logit regression model. Multiple categories are usu ally analysed with logit link and a multinomial distribution. Responses which are counts are usually analysed with a logarithmic link and a Poisson distribution: this is known as the pois son regression modeL. Such models also offer a very flexible approach to LongitudinaL data anaLysis, called discrete time analysis, in which the response is whether or not an event (e.g. marriage/separation/divorce) occurred in a specified time period. (NEW PARAGRAPH) This model based approach allows assess ment of the relationship between an outcome and a predictor variable (which may be con tinuous or categorical), taking account of other predictor variables. It is possible to test for relationships, derive overall goodness of fit measures and use diagnostic tools as part of expLoratory data anaLysis for assessing whether the model?s assumptions have been met. There is now a wide range of software for quantitative analysis. This is vital, as the procedures used to calibrate models do not permit exact analytical solutions as in standard regression, but require an iterative approach, which can be computationally expensive. kj (NEW PARAGRAPH) Suggested reading (NEW PARAGRAPH) Agresti (2002); Power and Xie (2000); Wrigley (1985b). (NEW PARAGRAPH)
cellular automata
Models of spatial phe nomena, usually comprising a raster grid of cells, each of which has a value representing its present ?state? on a variable of interest. algorithms with theoretically derived rules are applied to the initial system configuration to simulate changes. Run many times (each run is termed a ?generation'), the algorithm produces an evolving pattern. A classic example is the well known ?game of life', in which all cells are initially identified as either alive or dead (Conway, 1970); its algorithm's rules specify that, for example, if any cell has fewer than two live neighbours, it too will die. (NEW PARAGRAPH) Cellular automata have been used for sev eral decades in human geography to simulate spatial patterns and change as in Torsten Hagerstrand?s original work on the diffusion of innovations (see Morrill, 2005). Developments in computer technology, espe cially geographic information systems and geocomputation, have enabled large scale use of cellular automata models to simulate a wide range of environmental and other geographies (cf. agent based modelling). rj (NEW PARAGRAPH)
census
An enumeration, usually under taken within the state apparatus, to provide needed data for state purposes. The Latin word census translates as ?tax', giving a clear indication of the purpose of such enumer ations, the first of which are believed to take been taken in Egypt some 3,000 years ago. Many ad hoc censuses were taken before the nineteenth century as with the 1086 Domesday book in England. Since then, an increasing number of countries have con ducted regular (usually decennial) censuses as part of the development of statistics to inform the ever widening range of government decision making (Cullen, 1975). Censuses of population and housing are the most common, but separate censuses of, for example, agricul ture, construction, (local) governments, manu facturing, mining and retailing have been held. A few countries mainly in Scandinavia have replaced censuses by continuously updated, geocoded population registers. (NEW PARAGRAPH) Censuses are constitutionally mandated in some countries. In the USA, for example, Section Two of the First Article states that ?Representatives and direct taxes shall be apportioned among the several states ... according to their respective numbers?: the first census was to be conducted within three years of the constitution's acceptance, and ?within every subsequent term of ten years?. They have been conducted decennially since 1790, and their findings have sometimes been hotly disputed because of their implications as with the allocation of seats to the US House of Representatives after the 2000 census (Johnston, 2002: on the history of the US Census, see Eckler, 1972). (NEW PARAGRAPH) Although the primary role of a census is to collect factual information to inform public policy both current and future (such as population projections) nevertheless they cannot be considered ?neutral' tools. The data that they collect all refer to categories (occupa tional class, ethnicity etc.) that are social constructions, whose nature is determined by some theory of what should be measured, and how as with the main ethnicity categories now used in the US Census (White; Black or African American; American Indian and Alaskan Native; Asian; Native Hawaiian and Other Pacific Islander; Hispanic or Latino Origin) which dominate discourse about race and ethnicity there (Robbin, 2000; Yanow, (NEW PARAGRAPH) . Early US censuses generated consider able conflict between northern and southern states over counting slaves: southerners wanted to count them, because they would boost their entitlements to federal revenues and represen tation; northerners opposed to slavery were against. Eventually a compromise was reached, and slaves were counted as three fifths only of ?all other persons? until after the Civil War. ?Indians not taxed' were excluded entirely until 1936. A similar situation obtained in Australia, whose original constitution passed in 1900 included ?In reckoning the numbers of the people . . . aboriginal natives shall not be counted'. This remained the case until 1967, when voters overwhelmingly approved (91 per cent in favour: voting is compulsory in Australia) a referendum including the require ment that Aboriginals ?be counted in reckoning the population'. (NEW PARAGRAPH) Just as there is a politics and a sociology of official statistics, including censuses (on which see several chapters in Alonso and Starr, 1987), so there is also a politics and sociology of their use. Data can be deployed in a variety of ways to sustain particular cases, including partisan political projects as illustrated by the use of 2001 census data in the UK to portray the country's changing ethnic geog raphy in ways that, while not wrong, empha size findings that sustain a particular case (Dorling, 2005; Johnston and Poulsen, 2006). (NEW PARAGRAPH) The conduct of censuses is a major admin istrative task involving the distribution to and collection of forms from every address in the country, followed by the collation of large vol umes of data. That administration is in almost every case geographical in nature: the country is divided into small areas (variously termed ?collectors' districts', ?enumeration districts', etc.) in each of which data collection is over seen by a trained administrator (a role partly eliminated in some cases by use of postal and/ or on line Questionnaires). Those small areas may also be deployed as reporting units, with data made available to users at very fine spatial scales. (The average collection district at the 2001 New Zealand census contained 106 persons, for example.) Elsewhere, the smallest reporting units are specially designed to pro vide information about neighBourhoods in urban and separate settlements in rural areas, as with census tracts in the USA. For the 2001 UK census, geographers were involved in designing a three level hierarchy of output areas which are relatively homogeneous on two criteria dwelling type and tenure as well as meeting size and shape constraints and fitting within local authority boundaries: their aver age populations were 297, 1,513 and 7,234 persons, respectively (Rees, Martin and Williamson, 2002). (NEW PARAGRAPH) Although an increasing number of census authorities release data at such small spatial scaLes, thereby facilitating detailed geograph ical analyses (cf. factoriaL ecoLogy; segrega tion; sociaL area anaLYsis) some of value to policy makers, as in the identification of areas of sociaL excLusion within cities towards which programme money may be directed a major purpose of a census is to provide infor mation about and for sub national governmen tal and administrative units. These then form the context of much geographical analysis although geographers have been employed to define other spatial architectures for data dis semination that are commensurate with the contemporary spatial structure of economy and society, which may not be the case with administrative areas: examples are the use of commuting data to define metropoLitan areas in several countries. (NEW PARAGRAPH) Although the nature of the data collected and the spatial units for which they are (NEW PARAGRAPH) released are important constraints to spatiaL anaLysis, nevertheless censuses provide a wealth of information that has been deployed by geographers and others to portray many aspects of society not least through the production of atlases (e.g. Dorling and Thomas, 2004) notably, though not only, in popuLation, sociaL and urBan geography. In addition, census authorities are increasingly providing a wider range of material: public use micro samples of entirely anonymized individ ual records are released in some countries, for example, which may be linked across censuses to facilitate LongitudinaL data anaLYses. In some countries, too, the original manuscript census returns are made available (including on the inteEnet), perhaps 100 years after they were collected, allowing detailed analyses in historicaL geography not previously feasible. rj (NEW PARAGRAPH) Suggested reading (NEW PARAGRAPH) Alonso and Starr (1987); Eckler (1972); Open shaw (1995); Rees, Martin and Williamson (2002). (NEW PARAGRAPH)