Spatial Differentials Research Articles

Population density and spatial differentials in child mortality in Zimbabwe

Large regional variations in under-five mortality exist within many sub-Saharan countries. Population density as a potential explanatory factor for these regional variations has seldom been considered despite it being implicated as a determinant of mortality at other spatial scales. In Zimbabwe, the “Ndebele provinces”—Matabeleland North and South—have significantly lower levels of under-five mortality than the other (“Shona”) provinces. This regional differential is explored using the Zimbabwe Demographic and Health Survey and census data. Factors other than population density that may contribute to the differential are examined. After controlling for the effects of potentially confounding socio-economic, demographic and environmental variables using Cox regression models children aged 1–4 yr living in the Ndebele provinces continued to have a level of mortality 45% lower than their counterparts in the Shona provinces. The possibility that regional variations in health care provision and/or cultural factors contribute to the mortality differential is also examined and rejected. Population densities in the Ndebele provinces are of a far lower order than in the Shona provinces. The main causes of child mortality in Zimbabwe in the time period under consideration were diarrhoea, ALRI, measles and malaria. How population density may affect the transmission of these infections and, hence, mortality is discussed. It is suggested that population density may provide an explanation for the spatial variation in child mortality in Zimbabwe. The implications of changing population densities for child health in urban and rural sub-Saharan Africa are briefly considered.

Optical responses evoked by white matter stimulation in rat visual cortical slices and their relation to neural activities

To characterize optical responses (ORs) evoked by white matter (WM) stimulation in slices of rat visual cortex (VC) stained with voltage sensitive dyes, time course of ORs in each layer was investigated by recording ORs with a linearly aligned photodiode array, and the spatial patterns of the ORs at specified time after stimulation were investigated by a CCD camera in combination with stroboscopic illumination. The ORs recorded by the photodiode array were an increase in absorption at 700 nm and a decrease in the wavelength below 650 nm, suggesting that the ORs were dye related. The ORs were compared with field potentials (FPs) to clarify that neural events were represented by the ORs, and in support of this view, we found that the first order spatial differentials of ORs and that of FPs were in good agreement. We further compared ORs with intracellular responses, and found that the ORs mainly represent postsynaptic potentials (PSPs) of VC neurons except for the deeper part of layer VI, where a component representing action potentials in fibers stimulated directly was observed. The time-lapse imaging of ORs showed that excitation first propagated vertically up to layer I and subsequently in the horizontal direction along layers II-III and V-VI as in previous investigations. Spatio-temporal patterns of ORs under blockade of synaptic transmission were also investigated to reveal activity of fibers evoked by WM stimulation which produced such patterns of propagation.

The Role of Transportation Costs in the Economics of Commodity Markets

AbstractTransportation costs still play an important role in the economics of commodity markets. In this paper I present a theoretical framework aimed at describing spatial arbitrage under uncertainty; I analyze the effect of changing transport costs on different, yet related, variables: volume of trade, volatility of prices, and levels of spatial price differentials. As a tribute to Enke and Samuelson the model is referred to as the stochastic Enke‐Samuelson model. It provides predictions for variables (such as price volatilities or correlations) which cannot be defined in the deterministic framework of the standard spatial price equilibrium model. The statistical tests display a convergent array of evidence in favor of the model.

Socioeconomic and spatial differentials in mortality and means of committing suicide in New South Wales, Australia, 1985-91.

Analysis of suicide mortality in New South Wales, Australia is undertaken with reference to marital status and occupational status between 1986-89/90 and with reference to the principal means of committing suicide. Not currently married male manual workers were particularly at risk although marital status variations were significant with both genders and at different ages. Between 1985-91 male suicide mortality rates were significantly higher in inland non-metropolitan regions, especially among younger men, and were higher in inner areas of metropolitan Sydney. While there were no significant variations by marital status in the means of committing suicide there were variations between genders, and there were regional and social class variations in the use of guns with males. The use of guns was a factor in the elevated suicide mortality levels among inland rural youth and men, and among farmers and transport workers while the use of poisons was also significant with these occupational groups. The use of poisons was greater among persons committing suicide in the areas of elevated mortality in inner Sydney and the use of guns much lower.

Second‐order spectral local isotropy of the humidity and temperature fields in an urban area

AbstractA theoretical and experimental analysis of the humidity and temperature spatial differentials (δ/δxj,) in an urban area is presented. The local isotropy form of the spectra of the streamwise and vertical differentials of a scalar field is derived. The experimental results for the humidity and temperature fields in the lowest part of the urban boundary layer are in satisfactory agreement (at least in form under stable conditions) with the local isotropy model indicating that these fields can be locally isotropic. A strong anisotropy was observed at small wavenumbers of the vertical differentials spectra and it is probably connected with surface‐layer plumes. The analysis of the humidity and temperature differentials is extended to their co‐spectra and the spectra of the vertical differentials are compared to the streamwise ones. The comparison of the structure parameters of the temperature or the humidity field in the streamwise and the vertical direction, estimated using a spectral and a variance (structure function) method, showed no systematic departure from the isotropic prediction of equality.

Second-order spectral local isotropy of the humidity and temperature fields in an urban area

A theoretical and experimental analysis of the humidity and temperature spatial differentials (δ/δxj,) in an urban area is presented. The local isotropy form of the spectra of the streamwise and vertical differentials of a scalar field is derived. The experimental results for the humidity and temperature fields in the lowest part of the urban boundary layer are in satisfactory agreement (at least in form under stable conditions) with the local isotropy model indicating that these fields can be locally isotropic. A strong anisotropy was observed at small wavenumbers of the vertical differentials spectra and it is probably connected with surface-layer plumes. The analysis of the humidity and temperature differentials is extended to their co-spectra and the spectra of the vertical differentials are compared to the streamwise ones. The comparison of the structure parameters of the temperature or the humidity field in the streamwise and the vertical direction, estimated using a spectral and a variance (structure function) method, showed no systematic departure from the isotropic prediction of equality.

Migrant Inertia, Accessibility and Local Unemployment

A labour-markets model is constructed in which migration may exhibit 'distance deterrence' and 'cumulative inertia'. (Migration probabilities fall with distance and length of residence, respectively.) The combination of these two processes yields higher equilibrium unemployment rates in remote areas. Fewer out-migration opportunities in remote areas generate longer residence durations which become self-perpetuating (via cumulative inertia). Such areas accu- mulate net in-migrants until the local unemployment rate rises sufficiently to balance inflows and outflows. In equilibrium, local unemployment rates compensate for (endogenous) varia- tions in residence duration. Some evidence is presented for Britain which supports the pre- diction of higher unemployment in remote areas. inertia (or negative duration dependence) and distance deterrence in migration behaviour generates higher equilibrium unemployment rates in remote areas, all other things being equal. Cumulative inertia reflects a process whereby individuals form attachments to area, friends, job, etc., which grow over time. Distance deterrence arises because of increasing movement costs over longer distances, and friction in information flows about relevant opportunities. Both processes are intuitively plausible and have been tested empirically.' Clearly, both issues are likely to affect adjustment patterns in the face of shocks to labour markets. The argument advanced in this paper, however, and one that is perhaps not quite so obvious, is that the combination of the two processes can also affect the underlying equilibrium itself. The existence of persistent spatial differentials in unemployment is charac- teristic of most countries, and would appear to motivate areas of government policy. Various explanations for such differentials have been proposed. The analysis presented here is intended primarily to deepen our understanding of the causes of these sustained differentials, and hence to inform policy. Traditional explanations for sustained local unemployment differentials may be divided into three types. One argument is in terms simply of labour immobility-the perceived costs of moving outweigh the benefits, and hence labour market imbalances persist. Alternatively, one may combine mobile lab- our with spatial wage rigidities, such that equilibrium local unemployment patterns 'compensate' for local variation in wages and other exogenous factors (climate, environment, etc.) in people's preference functions. Finally, there is the issue of labour heterogeneity, e.g. by occupation; a 'compensating varia- tions' equilibrium may exist for each homogeneous class of labour, such that a region's aggregate unemployment rate reflects the local composition of

Housing Prices and Geographical Scale: Australian Cities in the 1980s

This paper examines the distribution of, and changes in, house prices in Australian cities during the 1980s, a period of considerable change in asset prices in general. The analysis is concerned to document the marked spatial variability of price movements and to relate these to processes of urban restructuring. Spatial variability is apparent at two scales: at the inter-metropolitan level as evidenced in trends across the major capital cities; and at the intra-metropolitan scale where differences between localities within one city, Melbourne, are identifiable. Substantial spatial differentials in both the level and in the rate of change over time of housing prices, have both efficiency and equity implications. Large regional price variations inhibit mobility and labour market adjustments; variations in the rate of increase both redistribute income and wealth in the form of capital gains, and differentially affect affordability levels. Analysis of different scales of price movement highlight the fact that some causal factors are common to all scales and some are scale dependent. At both scales, the most substantial rises and subsequent falls have been experienced in areas which have undergone of spatial restructuring consequent on a concentration of the effects of social and economic transformations. Changes in demand through long-term economic and social restructuring, however, were overwhelmed in the late 1980s by the deregulation of the financial system, which resulted in a greatly increased flow of finance into the housing sector. Despite high interest rates, a widespread belief that continued inflation would both raise the price of the commodity and reduce the real costs of borrowing, prompted a sharp but locationally specific rate of housing price increase followed by a slump in prices where the rises had been most extreme. The recession has increasingly affected all levels of the market and investment in housing generally is now being viewed much more cautiously.

Letters to the Editor

LETTERS TO THE EDITOR Dear Sir: May I comment on Neel's "Priorities in the Application of Genetic Principles to the Human Condition: A Dissident View," which appeared in your Autumn 1991 issue (vol. 35, pp. 49-67)? I have no quarrel with Neel's piece, except when he states on pp. 59—60 that: ". . . there is enough of a eugenic viewpoint still lurking in the background that if dramatic proposals to limit population growth are developed, the question of differential restraints on reproduction will arise. I reject such differential constraints, whether by individual or by country, as obfuscating the real issue." I'm afraid that we can no longer ignore the relationship between aggregate and differential fertility; rejecting it isjust sticking our heads in the sand. Neel seems too serious to do that. For example, the growth rate in Israel remains and will remain high as long as Jews and Arabs are fighting: the Jewish birthrate is high precisely because the Arab birthrate is high. There have been plenty of both scholarly and popular articles on this [1, 2, 3, 4]. The Israelis even have a phrase for it, which everybody there understands: "the demographic problem." One of the reasons Serbs give for slaughtering the Muslims in Bosnia is that the latter are trying to out-breed them (they aren't). Ditto for the Kosovo, where the Albanians do have a much higher birthrate. The Christians in Lebanon have not allowed a census since 1943 (!) for fear of discovery that their country has a Muslim majority. And all the trouble Nigeria has with its censuses is because of differential growth of different groups there. The initial eugenic policy in Singapore in 1984 failed because of resentments of the less educated and poorer groups, the majority of whom is Malay. Whereas the majority in Singapore is ethnic Chinese, but the fertility policy there is still pronatalist and for working women to get certain benefits (not a small amount, incidentally, $1500 + 20% of the woman's annual income for a 3d child and $1500 + 25% of the woman's annual income for a 4th child). To have more than four children, they must have at least 3 GCE O-level passes [for more details see 5, particularly pp. 74—75]. In fact, pronatalist policies are fairly common and have existed in France, East Germany (when there was such a country), Russia, Japan, and many of the countries with below replacement fertility (about 2.1 offspring per woman). There are many such countries in Europe and East Asia (including many of the coastal provinces of China: one wonders how long the "one-child" policy can last given the kind of spatial differentials there [6, pp. 151-152]). The Bharatiya Janata Party (BJP) in India, the main opposition party there, which may soon rule the world's Permission to reprint a letter printed in this section may be obtained only from the author. 1 56 Letters to the Editor second most populous country, is worried that the Muslims are growing faster than the Hindus, that it is the Hindus who practice family planning, not the Muslims. Even here in the U.S., the ZPG movement seems to be waking up to the problem of differential fertility [7]. Twenty-five years ago, Garrett Hardin wrote a famous article in Science, "The Tragedy of the Commons" (which I'm sure Neel has read), explaining why, if we are trying to reduce overall fertility, such attention to differential fertility is inevitable [8]. Given all the evidence reported here, can we ignore differential fertility when trying to get down aggregate fertility? I'm afraid such interest is more than just "lurking" in the background now. It's out in the open, is rarely eugenic, and has to be confronted. REFERENCES 1.Friedman, T. A forecast for Israel: More Arabs than Jews. New York Times, Al & A8, Oct. 19, 1987. 2.Nigen, E., and Nagi, M. Fertility patterns and differentials in Israel. Biology and Society 5:119-126, 1988. 3.Soffer, A. Population projections for the land of Israel. MiddleEastReview 20, 4:43-49, 1988. 4.Watson, R., and Kubic, M. Israel's Arab time bomb. Newsweek, 26-28...

Modelo de estructura de covarianzas para el análisis de las diferencias espaciales de la mortalidad mexicana

"This article examines some of the possible determinants of spatial mortality differentials in Mexico, on the basis of [a] path analytical model with latent variables." (SUMMARY IN ENG)

Frontiers, borders and border segmentation: Toward a conceptual clarification

In our desire to contribute meaningfully to borderlands research, we wander all over our material employing amorphous terms to characterize vague theoretical frameworks. As a rather newly established scientific field of inquiry, we tolerate some ambiguity, a few spongy concepts and a smattering of awkward or inapplicable methodologies in our rush to accumulate a ready reservoir of scientific data. But perhaps borderlands studies has reached a maturity level in which we, as borderlands scholars, might begin to turn our energies inward in an attempt to clarify and standardize our lexicon, our conceptual tools and our assumptions. Moreover, our publications seem to reflect two incongruous perspectives. In general, beginning border investigators focus on specific data assuming their material to be completely unique in substance, in time and in space. In contrast, more seasoned scholars with broader experience and resources at their command begin to generalize; ostensibly to synthesize but with the latent consequence of creating a specious border homogeneity which is unfounded and counterproductive. Both orientations are needed, however, to maintain some balance. This essay describes and clarifies three of the most common terms or concepts in borderlands studies: frontier, border and border segment. It will focus on four dimensions within each concept: spatial differentials, temporal variations, substantive issues and scholarly perspectives (including underlying assumptions). Because of space limitations, this essay will not be a comprehensive treatment but rather a selective survey indicating various dimensions and criteria which are reflected in scholarly applications of each concept.

Integration of United States, Thailand and Philippine Canned Tuna Markets

In this study we investigate price integration in the United States, Thailand and Philippine canned tuna markets by employing a dynamic model of spatial price differentials to determine how rapidly and completely price information is transmitted from one market to another over time. When the United States is assumed to be the central canned tuna market, we find that the Thai canned tuna market operates independently of price conditions in the United States. On the other hand, the Philippine market is well integrated with the United States market in the sense that a change in the United States price is quickly and effectively communicated to the Philippine market. These results are shown to have significant implications with regard to measures the United States might take to control the flow of canned tuna imports from Southeast Asia.

Social and spatial mortality differentials in Puerto Rico

"A factor analysis on twenty-six social and economic variables measured in the seventy-eight 'municipios' of [Puerto Rico] is used to build a socio-economic model that reveals regional disparities [in mortality]. Adult and infant mortality rates in the different regions are computed and show that disparities in public health do exist. In fact, it appears that the most developed urban areas have patterns of mortality similar to the more traditional rural areas. On the other hand the developing regions have pathogenic patterns." (SUMMARY IN ENG)

Urban-Rural Variations in the Structure of Manufacturing Production

This paper demonstrates that recent attempts to explain manufacturing shifts to nonmetropolitan areas can be synthesised into a capital vintage model of production. The result is a set of systematic differences between urban and rural production methods which are consistent with the locational implications of the manufacturing process cycle theory. The model is supported by the first comprehensive estimation of separate production functions for SMSAs and nonmetropolitan areas. Using Census data for the US from 1977, only SMSAs are shown to possess the significant agglomeration economies needed for product development and process innovation. Cost-competitive nonmetropolitan areas show much greater variation in input proportions due to spatial factor price differentials.

Testing Market Integration

AbstractA model of spatial price differentials for a tradable good is proposed which avoids the inferential dangers of received methods using static price correlations. The proposed method also extracts more information on the causes of price differentials from the same data. The method is illustrated using monthly rice price data for postindependence Bangladesh, including the very substantial regional price shocks during the 1974 famine. Impediments to market integration are indicated.

A three-dimensional computer model of domain wall motion in magnetic bubble materials

The existing equations of motion for a domain wall, as initially proposed by Slonczewski, are modified to permit treatment of a curved wall, with associated magnetization structure, in three-dimensions. The equations are solved numerically, by the so-called explicit method, to investigate dynamic wall conversion in the case of a translating bubble. A comparatively large grid matrix of 3552 points is used to define a bubble of radius 3 μm. To reduce the otherwise enormous computation time required by such a matrix (a) the Dufort-Frankel scheme for the 2nd order spatial partial differentials was modified to permit a feasible time step, and (b) a combination of analytical and numerical methods in the demagnetizing and stray field calculation were employed. The principle of the numerical solution is given, and examples of bubble transport are included to illustrate the capability of the method.

Labor Productivity and Local Industry Size: Further Issues in Assessing Agglomeration Economies

A great deal of attention recently has been focused on issues related to spatial differentials in labor productivity and the external economies of size.' Historically size economies have been related to scale economies and plant capacity.2 More recently industry and city size externalities, often termed localization and urbanization economies or simply agglomeration economies, have been analyzed to determine the direction and extent to which these size factors affect labor productivity and economies of scale [15]. A variety of issues characterize this literature, among which are the magnitude and direction of these effects, the appropriate estimating equation, and the relation between size, returns to scale, and the neutrality or factor bias of these effects. Despite their apparent success in identifying the relation between various size and productivity measures, past studies are not without their shortcomings. The purpose here is to address these issues and shortcomings in the context of estimating the external effects of industry size on labor productivity. Along the way we will indicate the shortcomings of approaches recently employed and consider the empirical importance of different measures of industry size and capital.' The next section reviews some of the shortcomings of past studies. They are of particular interest, for they are avoided by the approach and data of this study. The analytical approach is formulated in Section II which includes a report of the empirical analysis and its major findings. The final section summarizes and discusses the implications of this analysis.

Unemployment duration in the recession: The local labour market area scale

Green A. E. (1985) Unemployment duration in the recession: the local labour market area scale, Reg. Studies 19, 111–129. This paper examines spatial variations in the duration of uncompleted unemployment spells using median, lower and upper quartile duration measures within a local labour market area (LLMA) framework. Regional, hierarchical and functional differentials in unemployment duration during the recession are investigated using a nineteen-fold LLMA classification. It is discovered that pre-existing spatial differentials in unemployment duration experience were largely maintained; with longer durations recorded in the North than in the South, around Provincial Conurbations than in the London Metropolitan Region, at higher than at lower levels of the urban hierarchy, and in LLMAs with a manufacturing employment base than in those with a service or commercially oriented employment structure.

Cross-national tests of a third world development-migration paradigm: With particular attention to Venezuela

This paper amplifies a conceptual framework relating internal migration and development processes. This is first done by a cross-national comparison of regression parameters from interregional migration studies often different countries. Attention then turns to parallel analyses of interstate migration in Venezuela for three different time periods representing, approximately, 1940–1950, 1950–1960, and 1966–1971. These cross-national and temporal comparisons support the hypothesis that development systematically affects the role of distance separating origins and destinations, and of spatial differentials in urbanization levels, wages, unemployment, and education.

Spatial Differentials in Residential Displacement

Because existing research treats residential displacement as a consequence of housing market conditions associated with the urban core, the incidence of displacement is thought to be greater in: (1) metropolitan areas than nonmetropolitan areas, (2) the 'urban heartland' than other regions of the country, (3) central cities than suburbs, and (4) older, inner-city neighborhoods than younger, peripheral ones. Data from the US Annual Housing Survey are analyzed and case studies of individual cities are reviewed to test these four spatial hypotheses. While the strength of the evidence favoring the hypotheses depends in part upon the type of displacement rate employed, spatial contrasts in displacement generally appear to be less marked than the literature suggests. We attribute the lack of convincing support for the hypotheses to housing market pressures operating at the national level that generate involuntary mobility across all geographical sectors of the population.