Variation In Opportunities Research Articles

Can Anyone Be 'the' One? Evidence on Mate Selection from Speed Dating

Marriage data show a strong degree of positive assortative mating along a variety of attributes. But since marriage is an equilibrium outcome, it is unclear whether positive sorting is the result of preferences rather than opportunities. We assess the relative importance of preferences and opportunities in dating behaviour, using unique data from a large commercial speed dating agency. While the speed dating design gives us a direct observation of individual preferences, the random allocation of participants across events generates an exogenous source of variation in opportunities and allows us to identify the role of opportunities separately from that of preferences. We find that both women and men equally value physical attributes, such as age and weight, and that there is positive sorting along age, height, and education. The role of individual preferences, however, is outplayed by that of opportunities. Along some attributes (such as occupation, height and smoking) opportunities explain almost all the estimated variation in demand. Along other attributes (such as age), the role of preferences is more substantial, but never dominant. Despite this, preferences have a part when we observe a match, i.e., when two individuals propose to one another.

The medieval guild in cyberclothes: International dimensions of industry certification in information technology

To standardise protocols and knowledge so that they could draw on a borderless workforce, the information technology and telecommunications industries developed a new class of industry certification in the 1990s. As of mid-2000, approximately 2.5 million of these certifications had been earned by approximately 1.65 million people worldwide, half outside the US. These credentials are awarded by third-party examination, with three commercial testing firms operating at 5000 sites in 140 countries. Students prepare for the examinations in a variety of ways, including course work at commercial schools with both physical facilities and virtual presence in dozens of countries. This paper focuses on the status of IT certification in six countries (Australia, France, Germany, Russia, Spain and the UK), and the behaviour of six major certifying authorities (Microsoft, Cisco, SAP, Sun Microsystems, Oracle and Novell). It highlights (1) the ways that these certifying authorities behave in the countries at issue,(2) variations in opportunities for students to prepare for certification, by country, and (3)flexibility in the languages of instruction/preparation and the languages of examination in the IT certification system. Because this certification system lies outside formal tertiary systems, it is not subject to government data-gathering in any country, hence we know little about the backgrounds of those who seek/earn these credentials. The paper suggests and encourages three lines of research inquiry (basic descriptive tasks, comparative curriculum studies and assessment studies) that can enlighten the role of this growing parallel universe in tertiary education.

Push and pull factors in medical employees' turnover decisions: the effect of a careerist approach and organizational benefits on the decision to leave the job

This paper aims at understanding the relative impact of 'careerist' attitudes and organizational benefits on prospective turnover decisions. We argue that the push/pull trade-off between careerist attitudes and organizational benefits in relation to turnover is occupation-specific. This is assessed by combining the sociological hypothesis of occupational 'market viability' and the organizational focus on opportunities. Testing this assertion, we examined turnover decisions for four occupational groups from eight medical institutions located in seven geographic areas. Initial results showed occupational variations in the weight given to 'careerist' versus organizational benefits in turnover decisions. Results from two logistic regression models suggest that organizational benefits, in contrast to a 'careerist' orientation to work, restrain occupation-specific turnover behaviour, even when controlling for the effect of perceived opportunities. These results are interpreted in terms of the 'market viability' hypothesis which stresses occupational variations in opportunities. Economic fluctuations for peripheral employees possessing general, rather than firm-specific skills may improve, rather than limit employment alternatives and hence enhance rather than constrain turnover decisions.

Clustering of childhood acute leukaemia: The EUROCLUS Project.

The EUROCLUS Project is a collaborative endeavour in which incidence data for 13 35 1 cases of childhood leukaemia (CL) diagnosed between 1980 and 1989 in 17 countries were referenced to 26 425 small geographic areas and tested for evidence of spatial clustering. A second objective of EUROCLUS was to determine whether clustering of CL was associated with community demographic features and/or proximity to putative environmental hazards. The results show statistically significant evidence of clustering, but the magnitude is small (extra-Poisson variability = 1.65% of Poisson variability). Patterns of clustering are associated with population density and other demographic features which could indicate variations in opportunity for exposure to common infections. There is no consistent evidence that clusters are associated with proximity to nuclear facilities or other putative environmental hazards.

A functional analysis of a limestone grassland community

Abstract. We examine the potential of standardised data, mainly collected in the laboratory, to elucidate mechanisms of species coexistence, using a south‐facing, infertile, species‐ rich limestone grassland at Miller's Dale, Derbyshire, England as a model system. Standardised autecological data for 15 of the more important Miller's Dale species were obtained from the Integrated Screening Programme (ISP), and their functional attributes were reviewed in the context of a larger database, broadly representative of the British flora. Ordination of adult plant attributes demonstrated that the Miller's Dale species are strategically relatively uniform; most are slow‐growing, evergreen and tolerant of mineral nutrient deficiency. Ordination of seed attributes revealed more variety among the Miller's Dale species; the main axis of variation was from species with large, transient seeds (mostly grasses) to species with small, persistent seeds (mostly dicots). From the ordination we derive the predictions that germination of the latter species will be more temporally opportunistic and more inhibited by the presence of vegetation than the former. These predictions are consistent with data collected in experimental studies of seed persistence and germination at the site. These data suggest that spatial and temporal variation in opportunities for regeneration is an important mechanism contributing to the high species richness of dry limestone grasslands.

Reintegrating disadvantaged communities into the fabric of urban life: The role of community development

Abstract This article analyzes the extent to which systematic spatial variations in opportunities in metropolitan areas provide a persuasive rationale for three current strategies for stimulating the development of urban communities: enterprise zone programs, community development financial institutions, and community development corporations. It examines whether the strategies are appropriately designed to respond to serious deficiencies in opportunities in distressed inner cities and reviews available evidence about their efficacy in addressing those deficiencies. A review of the literature reveals that poor inner‐city neighborhoods, particularly communities of color, have unequal access to opportunities in numerous areas, including employment, credit and financial services, housing, neighborhood shopping, and social networks and services that provide access to information and resources. The limited best‐case evidence indicates that the three strategies vary greatly in their ability to address these ine...

Training Opportunities for Interlibrary Loan and Document Supply Staff

UNESCO commissioned the IFLA Program for the Universal Availability of Publications to examine the problems associated with training staffin the field of interlibrary loan and document supply. As part of the study, a survey was conducted of training opportunities offered by library associations and library schools to identify areas that are important for training and those that are actually taught. Wide variation in opportunities emerged even between different countries with advanced library systems. There was also a considerable discrepancy between topics taught and those considered important by practitioners of interlibrary loan. Lack of skills and materials was one of the major problems for trainers, as is the fact that others failed to perceive the importance of this aspect of information work

A Study of the Broadening of Droplet Size Distributions in Cumuli

Abstract Cloud droplets may take a variety of paths to reach some location in a cloud and therefore may encounter varying growth conditions. This paper examines the effect of these variations on broadening of the droplet size distribution in cumuli. Diffusional growth of a collection of droplets is studied in detail using measurements obtained during the Cooperative Convective Precipitation Experiment (CCOPE) from the University of Wyoming's King Air research aircraft. A technique is described by which these measurements may be converted to the frame of reference of a moving droplet. Entrainment processes that are associated with variations in vertical velocity appear to have the effect of intensifying fluctuations in integral radius, which in turn produce variations in the supersaturation encountered by the droplets and thus opportunities for variations in growth. Contributions to spectral broadening arise from turbulent structures in the cloud, producing variations in integral radius as well as in the c...

Aboriginal land rights in Australia: expectations, achievements and implications

Through land rights legislation Aborigines have now regained control, in varying degrees, over 12 per cent of Australia. This not only enhances their political power base but also, in theory, lays the foundation for increased social and economic independence. In practice the prospects are more limited. Aborigines in the south and east have obtained very little land; and while those in remote communities value the return of their land for spiritual and social reasons, most of that country is of little commercial worth. After tracing the background to Australian Aboriginal land rights, including differences in federal and state legislation, the paper focuses on the socio-economic implications of the return of the land. Detailed components considered include the reinforcement of spiritual and cultural identity and the development of mining and tourism as commercial enterprises. These demonstrate the wide variations in opportunities stemming from land rights and suggest that, while there have been significant positive gains, these inequalities prevent the process from achieving its ultimate end—a more just access to resources for Australian Aborigines.

Sex disparities in arrests by residence, race, and age: An assessment of the gender convergence/crime hypothesis

In this report we examine whether differences in sex disparities in crime exist by population subgroup (residence, race, and age), using arrest data from the Uniform Crime Reports. We assess the utility of the gender equality/crime position as an explanation of any differences that do exist, and we propose alternative interpretations of the data. The major finding is that for most offenses, the differences in the female percentage of arrests (FP/A) are borderline or negligible. In those few instances where differences in FP/A exist across the comparison groups, they appear to have little or no relation to levels of gender-role convergence from one subgroup to another. Instead, we conclude that the differences in FP/A can be explained better as due to differences in willingness to sanction female offenders, to variations in opportunities for traditional female-based consumer crimes, and/or to differing levels of economic vulnerability among some groups of females.

Alkaline Phosphatase and Phosphodiesterase Activities of the Brush Border Membrane of Four Strains of the Tapeworm, Hymenolepis diminuta

1981, loc. cit.), the female of H. americana is heterogametic, and the Z and W chromosomes are highly heteromorphic-the Z being mediocentric, the W subtelocentric. In degree of heteromorphism, the Z and W of Heterobilharzia differ considerably from the Z and W of schistosomes of the genus Schistosoma, where both are subtelocentric (Schistosoma mansoni and Schistosoma haematobium groups) or metaor submetacentric (Schistosoma japonicum and Schistosoma mekongi). The Z and W of Heterobilharzia are similar in general morphology to those of S. douthitti (Puente and Short, 1985, Journal of Parasitology 71: 345348), but differ in differentiation of heterochromatin as seen in C-banded preparations. We believe our lack of success in obtaining better C-bands probably resulted from less opportunity for variation of techniques, in turn due to a limited amount of material. This study was supported in part by the NSF Grant DEB 7816554. We are very grateful to Dr. Norman C. Ronald for supplying us with the infected snails used for this work. We also thank Messrs. James D. Liberatos and William H. Teehan for statistical and photographic help. a d Short, 1985, Journal of P rasit logy 348), but di fer in di ferentiation of het-

ChemInform Abstract: DESIGN, SYNTHESIS, AND X‐RAY DATA OF NOVEL POTENTIAL ANTIPSYCHOTIC AGENTS. SUBSTITUTED 7‐PHENYLQUINOLIZIDINES: STEREOSPECIFIC, NEUROLEPTIC, AND ANTINOCICEPTIVE PROPERTIES

AbstractDargestellt werden die Verbindungen (IX)‐(XI).

Movement patterns of yellow baboons (Papio cynocephalus): Central positioning of walking infants

AbstractAccording to DeVore and Washburn's protection theory of the spatial organization of moving baboon troops, walking infants, which are among the most vulnerable and least self‐sufficient of all troop members, should tend to occupy the troop's center. The protection theory is an ultimate hypothesis from which persistently recurring behavior is expected. Two troops living in Mikumi National Park, Tanzania, were compared with troops studied at other locations. Walking infants tended to occupy the center of their troop and to be underrepresented primarily in the frontal portion of progressions and secondarily in the rear. The lead position of progressions was analyzed using 82 walking infants, 11 troops, three locations, two species, and three studies involving eight or more observers employing somewhat different procedures at the different study sites. Despite so many opportunities for variation, 1,317 observations from these 11 troops did not produce a single instance in which a walking infant led the troop and very few in which one was in the frontal twelfth.

Patterns of Homogamy and the Field of Eligibles

Using retrospective reporting as a source of longitudinal data, an analysis is presented of varying degrees of homogamy between a homogeneous sample of engaged girls and three men with whom each had had a serious relationship. Evidence is presented which suggests that (a) there is a general tendency to become more homogamous through mate selection period on some dimensions (e.g., education) but to become less so on other dimensions (e.g., urbanity); (b) some of patterns more easily fit a theory based on variations in opportunities to meet different kinds of partners, others more easily fit a normative theory; (c) social changes during selection period (geographical or social mobility) influence level and pattern of homogamy. T he principle of homogamy in mate selection process is well established in sociological literature. Numerous studies have supported general proposition that dominant pattern in our society, even within framework of freedom of choice, is for marital partners to come from similar social categories. However, in spite of wealth of empirical evidence of this kind, we have not yet gone much beyond rather simple generalization that choices are usually made within broad social categories. We have stopped raising questions about social bases of mate selection seemingly because we assume that important sociological analysis has already been carried out by demonstrating homogamous patterns. In contrast, major thesis of this paper is that studies of homogamy have only begun to examine sociological aspects of mate selection. They have only posed problem, not solved it. There is nothing new in idea that problems remain in this area of inquiry. At least a decade ago Burgess and Locke' suggested that the actual factors determining assortative mating have not been studied, and they proceeded to list six possible explanations of empirical findings. Most of these explanations are of two types. The first type views patterns of mate selection as a function of opportunities. It explains similarities of mates on basis of residential segregation and differences in activity patterns of various social categories which limit range of contacts of any person to encounters with persons like himself. The second explanation is a normative one. It views patterns of similarity as result of preferences on part of chooser for persons like himself and/or enforcement of such homogamous choices through social sanctions. A recent treatment of some of issues by Katz and Hill attempts to combine two under a general norm-interaction theory.2 Although such a combination may have theoretic value, it makes even more apparent fact that same behavior may be result of very different antecedents. Conformity with pattern of homogamy, when At occurs, may be due to either limited opportunities or adherence to a norm. Simple reporting of pattern will not determine which is case.3 * The research was supported by a Faculty Research Grant from Duke University Research Council. I am indebted to Joel Smith and George Maddox for their helpful critique of an earlier version of this paper. 1 Ernest W. Burgess and Harvey J. Locke, The Family (New York: The American Book Company, 1953), p. 370. 2 Alvin M. Katz and Reuben Hill, Residential Propinquity and Marital Selection: A Review of Theory, Method, and Fact, Marriage and Family Living, 20 (1958), pp. 27-35. The first two assumptions of this theory are: 1. That marriage is normative. 2. That, within normative fields of eligibles, probability of marriage varies directly with probability of interaction. (p. 33) 3 These two factors occupy different positions in logic of explication of patterns of homogamy This content downloaded from 207.46.13.86 on Sat, 15 Oct 2016 04:25:02 UTC All use subject to http://about.jstor.org/terms

Linear Regression When the Standard Deviations of Arrays are Not All Equal

M ANY TEXTBOOKS on statistics consider regression only for the case when the standard deviations of all arrays are the same. The implication is that the formulas given are adequate for the cases met in practice and that, even though the standard deviations are not strictly equal, the usual formulas are still valid. Consequently many applications have been made to date without much attention to the equality of the standard deviations of the arrays.' It has been recognized since the days of Gauss that the standard deviations may vary from point to point. The methods for handling varying standard deviations are found in many writings on least squares and are used by some.2 Nevertheless, the ignorance of varying standard deviations is very widespread as well as the indifference to their importance. In any set of two-variable data in which the mean of one variable increases from zero or a small value to a large value for values of the other variable there is opportunity for the spread of the arrays to increase as the means of the arrays increase. An excellent example of this situation has been given by Dr. Brady3 who has shown that the standard deviations of the amounts expended on different phases of living have increased with income. Dr. S. C. Salmon has recently forcibly called attention4 to the increase of the standard deviations of agricultural yields with the increase in yield. Anything that grows, as a peach embryo, say, must start with size zero and zero standard deviation. As the size increases, the opportunity for variation comes into existence. Thus, peach embryos measured at different times show different standard deviations. In view of the many cases of practical importance where the standard deviations change from array to array, it becomes very important to consider regression freed of the assumption that the standard deviations df arrays are equal.

Selective Migration from Small Towns

N n r OT UNTIL two decades ago did Americans become seriously concerned with the question, Do the more intelligent or the less intelligent migrate? Following the world war, when immigration restriction was being discussed, there was much controversy over the differential native intelligence of various nationalities. Though it is generally admitted in scientific circles that there is no conclusive evidence of significant racial or national differences in mentality, intense controversy and speculation continue apace concerning the equality of internal migrants. Prior to I930 and even I935, it was usually claimed that the migration process operates to draw off the more intelligent from rural areas to towns and cities. Even today most writers will hesitantly conclude that there is selective migration favoring the city. The actual evidence is, however, far from clear. Many investigators have inferred intelligence from the amount of schooling or grades attained before migration with no allowance for variations in opportunity between social and economic classes, variations in the availability of schools in different types of communities, and variations in the standards of work in the different schools. Nor is it known how much additional schooling the migrants have received after migration. Moreover, there is some question as to whether the investigators have been interested in intelligence or achievement. Inferences as to intelligence based on the amount of schooling are challenged by those familiar with the operation of the educational system, and the correlation between intelligence and grades is often less than o.50 and seldom higher than o.60.1 And always one hears the query, there is selective migration, is it a biological selection or are the differences attributable solely to environment? If the selection is biological in nature, the problem is indeed acute, assuming that there is unfavorable selection for some areas, because there is danger of an entire area being depleted of leadership in which case the quality of stock may decrease. Such dysgenic effects must be watched and carefully guarded against if they are taking place, or even threaten to do so. On the other hand, assume: (I) that there is selective migration, and (2) that the differentials can be traced to environment. Though the quality of stock in any given area would not then be less, the trained or effective intelligence of the group which is being drained of the more intelligent-the better trained-would just as surely decrease. Social problems would arise just as quickly. Hence, regardless of the way in which selective migration may

The Feeding of Salmon Parr in the Cheshire Dee

Summary.The food of salmon parr in the Dee and its tributaries has been studied for two years. Comparison of stomach‐contents with the results of field collections shows that the fishes are indiscriminately carnivorous, and that their diet varies strictly in accordance with the number and relative accessibility of species present in the rivers. The sub‐äerial element in the food is important, especially in autumn, when leaf‐eating tree‐parasites fall into the rivers as the leaves decay and are swallowed in considerable numbers. Encouragement of the growth of riparian trees and shrubs is thus desirable.There is a marked seasonal cycle in feeding, which accurately corresponds with the records of fluctuations in growth derived from scale‐readings. This seasonal cycle seems to be directly dependent upon the life‐histories of the various food‐organisms, which determine their availability to the fishes: in the opinion of the writer there is no evidence of loss of appetite at any season, but merely of variations in opportunity.