Showing papers by "University of Chicago published in 1985"
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TL;DR: The presence of traders with superior information leads to a positive bid-ask spread even when the specialist is risk-neutral and makes zero expected profits as discussed by the authors, and the expectation of the average spread squared times volume is bounded by a number that is independent of insider activity.
5,902 citations
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TL;DR: The reserve tax on CD's is borne by bank borrowers as discussed by the authors, and it is assumed that bank borrowers are willing to pay higher interest rates than those on other securities of equivalent risk.
2,364 citations
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TL;DR: These models utilize the statistical relationship which exists between genotype‐environment interaction and genetic correlation to describe evolution of the mean phenotype under soft and hard selection in coarse‐grained environments.
Abstract: Studies of spatial variation in the environment have primarily focused on how genetic variation can be maintained. Many one-locus genetic models have addressed this issue, but, for several reasons, these models are not directly applicable to quantitative (polygenic) traits. One reason is that for continuously varying characters, the evolution of the mean phenotype expressed in different environments (the norm of reaction) is also of interest. Our quantitative genetic models describe the evolution of phenotypic response to the environment, also known as phenotypic plasticity (Gause, 1947), and illustrate how the norm of reaction (Schmalhausen, 1949) can be shaped by selection. These models utilize the statistical relationship which exists between genotype-environment interaction and genetic correlation to describe evolution of the mean phenotype under soft and hard selection in coarse-grained environments. Just as genetic correlations among characters within a single environment can constrain the response to simultaneous selection, so can a genetic correlation between states of a character which are expressed in two environments. Unless the genetic correlation across environments is ± 1, polygenic variation is exhausted, or there is a cost to plasticity, panmictic populations under a bivariate fitness function will eventually attain the optimum mean phenotype for a given character in each environment. However, very high positive or negative correlations can substantially slow the rate of evolution and may produce temporary maladaptation in one environment before the optimum joint phenotype is finally attained. Evolutionary trajectories under hard and soft selection can differ: in hard selection, the environments with the highest initial mean fitness contribute most individuals to the mating pool. In both hard and soft selection, evolution toward the optimum in a rare environment is much slower than it is in a common one. A subdivided population model reveals that migration restriction can facilitate local adaptation. However, unless there is no migration or one of the special cases discussed for panmictic populations holds, no geographical variation in the norm of reaction will be maintained at equilibrium. Implications of these results for the interpretation of spatial patterns of phenotypic variation in natural populations are discussed.
2,019 citations
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TL;DR: The authors examined the cross-sectional relation between the mean growth rate of real product (growth) and variables suggested by the theoretical literature and found that Barro's hypothesis that the variability of monetary shocks adversely affects growth receives strong support.
1,713 citations
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TL;DR: In this article, the authors present a simple yet general method of calculating asymptotically correct standard errors in T-S models, which may be applied even when joint estimation methods, such as full information maximum likelihood, are inappropriate or computationally infeasible.
Abstract: A commonly used procedure in a wide class of empirical applications is to impute unobserved regressors, such as expectations, from an auxiliary econometric model. This two-step (T-S) procedure fails to account for the fact that imputed regressors are measured with sampling error, so hypothesis tests based on the estimated covariance matrix of the second-step estimator are biased, even in large samples. We present a simple yet general method of calculating asymptotically correct standard errors in T-S models. The procedure may be applied even when joint estimation methods, such as full information maximum likelihood, are inappropriate or computationally infeasible. We present two examples from recent empirical literature in which these corrections have a major impact on hypothesis testing.
1,601 citations
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TL;DR: Genetic models are constructed which allow inbreeding depression to change with the mean selfing rate in a population by incorporating both mutation to recessive and partially dominant lethal and sublethal alleles at many loci and mutation in quantitative characters under stabilizing selection.
Abstract: The amounts of inbreeding depression upon selfing and of heterosis upon outcrossing determine the strength of selection on the selfing rate in a population when this evolves polygenically by small steps. Genetic models are constructed which allow inbreeding depression to change with the mean selfing rate in a population by incorporating both mutation to recessive and partially dominant lethal and sublethal alleles at many loci and mutation in quantitative characters under stabilizing selection. The models help to explain observations of high inbreeding depression (> 50%) upon selfing in primarily outcrossing populations, as well as considerable heterosis upon outcrossing in primarily selfing populations. Predominant selfing and predominant outcrossing are found to be alternative stable states of the mating system in most plant populations. Which of these stable states a species approaches depends on the history of its population structure and the magnitude of effect of genes influencing the selfing rate.
1,601 citations
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TL;DR: In this article, the propagation of strings in background fields, including the effects of metric, antisymmetric tensor, and dilaton expectation values, as well as gauge field backgrounds in the case of heterotic strings, is studied.
1,391 citations
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TL;DR: This is the first demonstration of a transforming gene in Epstein-Barr virus, a ubiquitous human pathogen associated with neoplasia, which is likely to account for many aspects of EBV induced cell transformations.
1,237 citations
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TL;DR: In this article, two families of mixed finite elements, one based on triangles and the other on rectangles, are introduced as alternatives to the usual Raviart-Thomas-Nedelec spaces.
Abstract: Two families of mixed finite elements, one based on triangles and the other on rectangles, are introduced as alternatives to the usual Raviart-Thomas-Nedelec spaces. Error estimates inL 2 (Ω) andH ?5 (Ω) are derived for these elements. A hybrid version of the mixed method is also considered, and some superconvergence phenomena are discussed.
1,213 citations
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TL;DR: Methods for estimating the impact of training on earnings when non-random selection characterizes the enrollment of persons into training are presented and the robustness of the estimators to choice-based sampling and contamination bias is examined.
1,020 citations
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TL;DR: In this paper, a recursive transition network model is discussed that integrates story grammar, causal chain, causal network, and hierarchical problem-solving approaches to story representation for predicting data on immediate and delayed recall, summarization, and judged importance of events.
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TL;DR: This paper argued that gestures and speech are parts of the same psychological structure and share a computational stage, based on the very close temporal, semantic, pragmatic, pathological, and developmental parallels between speech and referential and discourse-oriented gestures.
Abstract: In this article I argue that gestures and speech are parts of the same psychological structure and share a computational stage. The argument is based on the very close temporal, semantic, pragmatic, pathological, and developmental parallels between speech and referential and discourse-oriented gestures. Most of the article consists of a description of these parallels. A concept that unites outer speech and gesture is the hypothesis of inner speech.
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TL;DR: A technique due to A. Joffe (1974) is applied and deterministic construction in fast parallel time of various combinatorial objects whose existence follows from probabilistic arguments is obtained.
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TL;DR: On etudie le probleme de Dirichlet dans un domaine borne Ω de R n a frontiere lisse ∂Ω:F(D 2 u)=ψ dans Ω, u=φ sur ∂ Ω as discussed by the authors.
Abstract: On etudie le probleme de Dirichlet dans un domaine borne Ω de R n a frontiere lisse ∂Ω:F(D 2 u)=ψ dans Ω, u=φ sur ∂Ω
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01 Dec 1985TL;DR: The aim of this paper is to replace most of the (proven and unproven) group theory of [BS] by elementary combinatorial arguments and defines a new hierarchy of complexity classes “just above NP
Abstract: In a previous paper [BS] we proved, using the elements of the theory of nilpotent groups, that some of the fundamental computational problems in matriz groups belong to NP. These problems were also shown to belong to coNP, assuming an unproven hypothesis concerning finite simple groups.The aim of this paper is to replace most of the (proven and unproven) group theory of [BS] by elementary combinatorial arguments. The result we prove is that relative to a random oracle B, the mentioned matrix group problems belong to (NP∩coNP)B.The problems we consider are membership in and order of a matrix group given by a list of generators. These problems can be viewed as multidimensional versions of a close relative of the discrete logarithm problem. Hence NP∩coNP might be the lowest natural complexity class they may fit in.We remark that the results remain valid for black box groups where group operations are performed by an oracle.The tools we introduce seem interesting in their own right. We define a new hierarchy of complexity classes AM(k) “just above NP”, introducing Arthur vs. Merlin games, the bounded-away version of Papdimitriou's Games against Nature. We prove that in spite of their analogy with the polynomial time hierarchy, the finite levels of this hierarchy collapse to AM=AM(2). Using a combinatorial lemma on finite groups [BE], we construct a game by which the nondeterministic player (Merlin) is able to convince the random player (Arthur) about the relation [G]=N provided Arthur trusts conclusions based on statistical evidence (such as a Slowly-Strassen type “proof” of primality).One can prove that AM consists precisely of those languages which belong to NPB for almost every oracle B.Our hierarchy has an interesting, still unclarified relation to another hierarchy, obtained by removing the central ingredient from the User vs. Expert games of Goldwasser, Micali and Rackoff.
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TL;DR: In this paper, the authors focus on the aspect of an economic system on which they focus is its architecture, that is, how the decision making units are organized together within a system, who gathers what information, and who communicates what with whom.
Abstract: We present some new ways of looking at economic systems. The aspect of human behavior which we emphasize is that individuals' judgments entail errors (they sometimes reject good projects and accept bad projects). The aspect of an economic system on which we focus is its architecture; that is, how the decision making units are organized together within a system, who gathers what information, and who communicates what with whom. The architecture of a system affects its performance not only because it influences the nature of errors which individuals make within the system, but also because it has a critical effect on the aggregation of individuals' errors. We analyze and compare the performance of two polar architectures, with decentralized (polyarchical) versus centralized (hierarchical) decision making authorities. Also, we discuss several extensions of our analysis.
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TL;DR: For example, this article found that black teenagers living in metropolitan areas of the United States initiate sexual intercourse at earlier ages than other teenagers and have higher rates of premarital pregnancy.
Abstract: Black teenagers living in metropolitan areas of the United States initiate sexual intercourse at earlier ages than other teenagers and have higher rates of premarital pregnancy. Ethnographic studies of black families have claimed that economic uncertainties cause young blacks to delay marriage, while many young women achieve adulthood through premarital parenthood. It is also probable that girls who grow up in a female-headed family or who see their sisters become teenage parents are more likely to accept single-parenthood as a way to achieve adult status. These studies have suggested that ghetto neighborhoods are characterized by loosely defined and enforced norms of sexual behavior and age and sex compositions conducive to juvenile deviance. These features of ghetto life make it difficult for parents to regulate successfully their children's behaviors. As a consequence, residents of ghetto neighborhoods are expected to initiate sexual intercourse at earlier ages and to have higher rates of accidental premarital pregnancy than other teens. These hypotheses have received limited support in previous demographic research on teenage fertility. In this paper, these ethnographic explanations of the fertility behaviors of black adolescents are tested, using data from a random sample of more than 1,000 black females aged 13-19 who lived in the city of Chicago in 1979. This analysis improves on previous demographic research by both measuring the total effects of these variables on fertility and decomposing them into components due to effects on rates of initial sexual
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TL;DR: In this article, a model of how people make judgments under ambiguity in tasks where data come from a source of limited, but not exactly known reliability, is proposed, which assumes an anchoring-and-adjustment process in which data provides the anchor, and adjustments are made for what might have been.
Abstract: : Ambiguity results from having limited knowledge of the process that generates outcomes. It is argued that many real-world processes are perceived to be ambiguous; moreover, as Ellsberg demonstrated, this poses problems for theories of probability operationalized via choices amongst gambles. A descriptive model of how people make judgments under ambiguity in tasks where data come from a source of limited, but not exactly known reliability, is proposed. The model assumes an anchoring-and-adjustment process in which data provides the anchor, and adjustments are made for what might have been. The latter is modeled as the result of a mental simulation process that incorporates the unreliability of the source and one's attitude toward ambiguity in the circumstances. A two-parameter model of this process is shown to be consistent with: Keynes' idea of the weight of evidence, the non-additivity of complementary probabilities, current psychological theories of risk, and Ellsberg's original paradox. The model is tested in four experiments at both the individual and group levels. In experiments 1-3, the model is shown to predict judgments quite well; in experiment 4, the inference model is shown to predict choices between gambles. The results and model are then discussed with respect to the importance of ambiguity in assessing perceived uncertainty; the use of cognitive strategies in judgments under ambiguity; the role of ambiguity in risky choice; and extensions of the model. (Author)
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TL;DR: A bimodal distribution of outCrossing rates was observed for natural plant populations, with more primarily selfing and primarily outcrossing species, and fewer species with intermediate outcrossed rate than expected by chance.
Abstract: A bimodal distribution of outcrossing rates was observed for natural plant populations, with more primarily selfing and primarily outcrossing species, and fewer species with intermediate outcrossing rate than expected by chance. We suggest that this distribution results from selection for the maintenance of outcrossing in historically large, outcrossing populations with substantial inbreeding depression, and from selection for selfing when increased inbreeding, due to pollinator failure or population bottlenecks, reduces the level of inbreeding depression. Few species or populations are fixed at complete selfing or complete outcrossing. A low level of selfing in primarily outcrossing species is unlikely to be selectively advantageous, but will not reduce inbreeding depression to the level where selfing is selectively favored, particularly if accompanied by reproductive compensation. Similarly, occasional outcrossing in primarily selfing species is unlikely to regularly provide sufficient heterosis to maintain selection for outcrossing through individual selection. Genetic, morphological and ecological constraints may limit the potential for outcrossing rates in selfers to be reduced below some minimum level.
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01 Jan 1985TL;DR: In this paper, the authors focus on the study of parametric and nonparametric methods for estimating the effect size (standardized mean difference) from a single experiment, which is based on the belief that the population effect size is actually the same across studies.
Abstract: This chapter focuses on the study of parametric and nonparametric methods for estimating the effect size (standardized mean difference) from a single experiment. It is important to recognize that estimating and interpreting a common effect size is based on the belief that the population effect size is actually the same across studies. Otherwise, estimating a mean effect may obscure important differences between the studies. The chapter discusses several alternative point estimators of the effect size δ from a single two-group experiment. These estimators are based on the sample standardized mean difference but differ by multiplicative constants that depend on the sample sizes involved. Although the estimates have identical large sample properties, they generally differ in terms of small sample properties. The statistical properties of estimators of effect size depend on the model for the observations in the experiment. A convenient and often realistic model is to assume that the observations are independently normally distributed within groups of the experiment.
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TL;DR: In this article, it was shown that the decline of a hegemonic power may actually lead to an outcome both collectively superior and distributively preferable than when the hegemon was at the apogee of its power.
Abstract: Hegemonic stability theory has been advanced as an explanation of successful cooperation in the international system. The basis of this “hegemonic cooperation” is the leadership of the hegemonic state; its appeal rests on attractive implications about distribution. However, two distinct strands of the theory (“coercive” and “benevolent”) must be distinguished. These strands have different conceptions of hegemony and the role of hegemonic leaders and so have different implications. Both require us to assume that the underlying international issues are public goods and that the international system does not allow for collective action. The former assumption limits the theory's range of application while the likely failure of the latter means that the theory may be wrong even within this more limited range. Simple formal models demonstrate a conclusion completely at odds with hegemonic stability theory: the decline of a hegemonic power may actually lead to an outcome both collectively superior and distributively preferable than when the hegemon was at the apogee of its power. Thus hegemonic stability is, in fact, only a special case of international cooperation. Understanding cooperation in general requires less restrictive assumptions.
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TL;DR: In this article, the authors identify causal relations between all pairs of events in six folktales, using context-dependent, logical criteria of necessity, and counterfactual tests of the form: If event A had not occurred, then, in the circumstances of the story, event B would not have occurred.
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TL;DR: In this paper, the set of σ-conjugacy classes in a connected reductive group G over a P-adic field is defined, and a concrete description of the set B(G) is given.
Abstract: Let F be a P-adic field, let L be the completion of a maximal unramified extension of F, and let σ be the Frobenius automorphism of L over F. For any connected reductive group G over F one denotes by B(G) the set of σ-conjugacy classes in G(L) (elements x,y in G(L) are said to be σ-conjugate if there exists g in G(L) such that g-1κ σ(g)=y. One of the main results of this paper is a concrete description of the set B(G) (previously this was known only in the quasi-split case).
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TL;DR: In this article, a model of competition among special interest groups for political influence is presented, where each active group exerts pressure to affect its taxes and subsidies, where activities of different groups are related by the equality between total tax collections and total tax subsidies.
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TL;DR: In this article, the stability of first-order dissipative relativistic fluid theories including the theories of Eckart and of Landau and Lifshitz as special cases is studied.
Abstract: We consider the stability of a general class of first-order dissipative relativistic fluid theories which includes the theories of Eckart and of Landau and Lifshitz as special cases. We show that all of these theories are unstable in the sense that small spatially bounded departures from equilibrium at one instant of time will diverge exponentially with time. The time scales for these instabilities are very short; for example, water at room temperature and pressure has an instability with a growth time scale of about ${10}^{\mathrm{\ensuremath{-}}34}$ seconds in these theories. These results provide overwhelming motivation (we believe) for abandoning these theories in favor of the second-order (Israel) theories which are free of these difficulties.
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TL;DR: In this paper, the authors discuss the realization of superconformal invariance in two dimensional quantum field theory and show that the Z2 odd sector of the tricritical Ising model is a representation of the Ramond algebra.
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TL;DR: In this article, the authors reconcile three stylized facts about capital budgeting in firms and show that they are tied to the presence of asymmetric information among the several members of the firm, each with his or her own objectives and decisions.
Abstract: This paper reconciles three stylized facts about capital budgeting in firms and shows that they are tied to the presence of asymmetric information among the several members of the firm, each with his or her own objectives and decisions. The facts of interest are:
1. The existence of organizational slack.
2. The "rationing" of resources within organizations.
3. The stated "cut off rate" for accepting capital projects in firms is often greater than the market rate of interest.
Organizational slack is defined as the excess of resources allocated over the minimum necessary to accomplish the tasks assigned. Resource rationing is defined as the under-allocation of resources; i.e., an increase in the amount allocated would generate revenues in excess of its costs. Rationing and slack are both manifestations of ex post inefficiencies. An LP model is used to show that these inefficiencies can occur in ex ante efficient organizational designs when asymmetric information is present. The optimal allocation policy involves a hurdle rate criterion in which the hurdle rate is strictly in excess of the cost of capital, thus inducing rationing in some states of the world. Typically, resources are optimally allocated such that slack exists in other states. The optimal allocation policy trades off these two inefficiencies.
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TL;DR: Developpement d'une nouvelle spectroscopie permettant l'etude des variations de la chaleur massique des liquides avec la frequence avec the frequence.
Abstract: The glass transition has historically been viewed as an anomaly involving the specific heat of supercooled liquids. It is also associated with a divergence of the relaxation times for liquid rearrangements. We have developed a new spectroscopy to study the frequency dependence of the specific heat of liquids which connects these two approaches. We report measurements as a function of temperature of the distribution of relaxation times which are directly responsible for the glass transition in glycerol.
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TL;DR: The only role thus far identified for coenzyme B12 in these reactions--namely, that of a free radical precursor--reflects the weakness, and facile dissociation, of the cobalt-carbon bond.
Abstract: Coenzyme B12 serves as a cofactor in various enzymatic reactions in which a hydrogen atom is interchanged with a substituent on an adjacent carbon atom. Measurement of the dissociation energy of the coenzyme's cobalt-carbon bond and studies of the rearrangement of model free radicals related to those derived from methylmalonyl-coenzyme A suggest that these enzymatic reactions occur through homolytic dissociation of the coenzyme's cobalt-carbon bond, abstraction of a hydrogen atom from the substrate by the coenzyme-derived 5'-deoxyadenosyl radical, and rearrangement of the resulting substrate radical. The only role thus far identified for coenzyme B12 in these reactions--namely, that of a free radical precursor--reflects the weakness, and facile dissociation, of the cobalt-carbon bond.
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TL;DR: In this paper, the authors relax the assumptions of 2 × 2 games and develop an alternate model of the coordination game, which has very different properties from those found in Prisoners' Dilemma.
Abstract: The study of political institutions in general and international cooperation in particular has been beneficially influenced by the Prisoners' Dilemma (PD) game model, but there is a mistaken tendency to treat PD as representing the singular problem of collective action and cooperation. By relaxing the assumptions of 2 × 2 games and developing an alternate model of the coordination game, I show how some cooperation problems have very different properties from those found in PD. The analytical results of the two games are compared across several important dimensions: number of strategies available, number of iterations of the game, numbers of players, and the distribution of power among them. The discussion is illustrated with specific problems of international cooperation, and the implications of alternative cooperation problems for the formation and performance of international regimes are explored. The basic solutions for PD and coordination have divergent ramifications for the institutionalization, stability, and adaptability of regimes and for the role of hegemony in the international system. However, the coordination model does not replace the PD model but complements and supplements it as a way to understand the diversity of political institutions. These results are widely applicable to areas of politics beyond international relations.