Confidence bounds for the sensitivity lack of a less specific diagnostic test, without gold standard

We consider the problem of comparing two diagnostic tests based on a sample of paired test results without true state determinations, in cases where the second test can reasonably be assumed to be at least as specific as the first. For such cases, we provide two informative confidence bounds: A lower one for the prevalence times the sensitivity gain of the second test with respect to the first, and an upper one for the sensitivity of the first test. Neither conditional independence of the two tests nor perfectness of any of them needs to be assumed. An application of the proposed confidence bounds to a sample of 256 pairs of laboratory test results for toxigenic Clostridium difficile provides evidence for a dramatic sensitivity gain through first appropriately culturing C. difficile from stool samples before applying an enzyme-immuno-assay.     

Efficient paired choice designs with fewer choice pairs

For paired choice experiments, two new construction methods of designs are proposed for the estimation of the main effects. In many cases, these designs require about 30–50% fewer choice pairs than the existing designs and at the same time have reasonably high D-efficiencies for the estimation of the main effects. Furthermore, as against the existing efficient designs, our designs have higher D-efficiencies for the same number of choice pairs.     

Density estimates of low bias

Two methods are given for adapting a kernel density estimate to obtain an estimate of a density function with bias O(h ^p ) for any given p, where h = h(n) is the bandwidth and n is the sample size. The first method is standard. The second method is new and involves use of Bell polynomials. The second method is shown to yield smaller biases and smaller mean squared errors than classical kernel density estimates and those due to Jones et al. (Biometrika 82:327–338, 1995).     

Regularity in overlapping generations exchange economies

In this paper we develop a regularity theory for stationary overlapping generations economies. We show that generically there is an odd number of steady states in which a non-zero amount of nominal debt (fiat money) is passed from generation to generation and an odd number in which there is no nominal debt. We are also interested in non-steady state perfect foresight paths. As a first step in this direction we analyze the behavior of paths near a steady state. We show that generically they are given by a second order difference equation that satisfies strong regularity properties. Economic theory alone imposes little restriction on those paths: With n goods and consumers who live for m periods, for example, the only restriction on the set of paths converging to the steady state is that they form a manifold of dimension no less than one, no more than 2nm.     

An equivalence theorem for a differential information economy

In a pure exchange economy with differential information and a finite set of traders, physical commodities and states of nature, we characterize the Walrasian expectations or Radner equilibria by using the veto power of the grand coalition. We prove that an allocation x is a Radner equilibrium allocation if and only if it is “privately non-dominated” by the grand coalition in every economy obtained by perturbing the original initial endowments in the direction of x. The first and second welfare theorems become particular cases of our main result. Since the deterministic Arrow–Debreu–McKenzie model is a special case of the differential information economy model we also provide a new characterization of the Walrasian equilibria.     

On bootstrapping the mode in the nonparametric regression model with random design

In the nonparametric regression model with random design and based on i.i.d. pairs of observations (X _i, Y _i), where the regression function m is given by m(x)=?(Y _i|X _i=x), estimation of the location θ (mode) of a unique maximum of m by the location of a maximum of the Nadaraya-Watson kernel estimator for the curve m is considered. In order to obtain asymptotic confidence intervals for θ, the suitably normalized distribution of is bootstrapped in two ways: we present a paired bootstrap (PB) where resampling is done from the empirical distribution of the pairs of observations and a smoothed paired bootstrap (SPB) where the bootstrap variables are generated from a smooth bivariate density based on the pairs of observations. While the PB requires only relatively small computational effort when carried out in practice, it is shown to work only in the case of vanishing asymptotic bias, i.e. of “undersmoothing” when compared to optimal smoothing for mode estimation. On the other hand, the SPB, although causing more intricate computations, is able to capture the correct amount of bias if the pilot estimator for m oversmoothes. Received: May 2000     

Globalization and business cycle transmission

The paper uses long-run GDP data for developed countries drawn from Maddison [Maddison, A. (2003). The world economy—Historical statistics. Paris: OECD Development Centre] to generate deviation cycles for the period from 1870 to 2001. The cyclical deviates are examined for their bilateral cross-correlation values in three separate periods, those of the first globalization wave (1870–1914), the period of the “bloc economy” (1915–1959) and for the period of the second globalization (1960–2001). Cluster analysis is applied and the McNemar test is used to test for the relative coherence of alternative groupings of countries in the three periods. The bloc economy period emerges as one that features some well-defined sub-global clusters, where the second globalization period does not, the first globalization period lying between the two in this respect. The second globalization period shows a generally higher level of cross-correlations and a lower variance than the other two periods. The features uncovered suggest that the second globalization period is indeed one that comprises a more inclusive world economy than ever before.     

Comprehensive analysis of market conditions in the foreign exchange market

We investigate quotation and transaction activities in the foreign exchange market for every week during the period of June 2007 to December 2010. A scaling relationship between the mean values of number of quotations (or number of transactions) for various currency pairs and the corresponding standard deviations holds for a majority of the weeks. However, the scaling breaks in some time intervals, which is related to the emergence of market shocks. There is a monotonous relationship between values of scaling indices and global averages of currency pair cross-correlations when both quantities are observed for various window lengths ?? t.     

Seasonality and non-linear price effects in scanner-data-based market-response models

Scanner data for fast moving consumer goods typically amount to panels of time series where both N and T are large. To reduce the number of parameters and to shrink parameters towards plausible and interpretable values, Hierarchical Bayes models turn out to be useful. Such models contain in the second level a stochastic model to describe the parameters in the first level.     

Second‐gift behaviour of first‐time donors to charity: an empirical study

• This study examined the second‐time charity giving behaviour of a sample of 551 young people during a 2‐year period following the occurrence of their first ever significant donation. It explored the factors that encouraged an individual to make a second gift, the probabilities that a donation would be made within certain time intervals after the initial gift (3 months, 6 months, a year, etc.) and the variables that influenced whether the second donation would go to the charity receiving the person's first gift or to a different charity. Relevant issues were investigated via a Cox proportional hazards regression analysis and through a binary logistic regression. Covariates employed in the course of the study included the degree of emotional uplift a person experienced and the level of mind‐set change that took place consequent to a first donation, donor confusion with the range and variety of charities available and the reputation and image congruity of the second charity to which the participant had contributed. The roles of personal inertia and social pressure when making donation decisions were also examined.

Copyright © 2008 John Wiley & Sons, Ltd.     

School choice: Nash implementation of stable matchings through rank-priority mechanisms

We consider school choice problems (Abdulkadiroğlu and Sönmez, 2003) where students are assigned to public schools through a centralized assignment mechanism. We study the family of so-called rank-priority mechanisms, each of which is induced by an order of rank-priority pairs. Following the corresponding order of pairs, at each step a rank-priority mechanism considers a rank-priority pair and matches an available student to an unfilled school if the student and the school rank and prioritize each other in accordance with the rank-priority pair. The Boston or immediate acceptance mechanism is a particular rank-priority mechanism. Our first main result is a characterization of the subfamily of rank-priority mechanisms that Nash implement the set of stable matchings (Theorem 1). Our second main result is a strong impossibility result: under incomplete information, no rank-priority mechanism implements the set of stable matchings (Theorem 2).     

Equilibria in a class of aggregative location games

Consider a multimarket oligopoly, where firms have a single license that allows them to supply exactly one market out of a given set of markets. How does the restriction to supply only one market influence the existence of equilibria in the game? To answer this question, we study a general class of aggregative location games where a strategy of a player is to choose simultaneously both a location out of a finite set and a non-negative quantity out of a compact interval. The utility of each player is assumed to depend solely on the chosen location, the chosen quantity, and the aggregated quantity of all other players on the chosen location. We show that each game in this class possesses a pure Nash equilibrium whenever the players’ utility functions satisfy the assumptions negative externality, decreasing marginal utility, continuity, and Location–Symmetry. We also provide examples exhibiting that, if one of the assumptions is violated, a pure Nash equilibrium may fail to exist.     

Strategy-proofness and population-monotonicity for house allocation problems

We study a simple model of assigning indivisible objects to agents, such as dorm rooms to students, or offices to professors, where each agent receives at most one object and monetary compensations are not possible. For these problems population-monotonicity, which requires that agents are affected by population changes in the same way, is a compelling property because tentative assignments are made in many typical situations, which may have to be revised later to take into account the changing population. We completely describe the allocation rules satisfying population-monotonicity, strategy-proofness, and efficiency. The characterized rules assign the objects by an iterative procedure in which at each step no more than two agents “trade” objects from their hierarchically specified “endowments.”     

A survey on pickup and delivery problems

This paper is the second part of a comprehensive survey on routing problems involving pickups and deliveries. Basically, two problem classes can be distinguished. The first part dealt with the transportation of goods from the depot to linehaul customers and from backhaul customers to the depot. The second part now considers all those problems where goods are transported between pickup and delivery locations, denoted as Vehicle Routing Problems with Pickups and Deliveries (VRPPD). These are the Pickup and Delivery Vehicle Routing Problem (PDVRP – unpaired pickup and delivery points), the classical Pickup and Delivery Problem (PDP – paired pickup and delivery points), and the Dial-A-Ride Problem (DARP – passenger transportation between paired pickup and delivery points and user inconvenience taken into consideration). Single as well as multi vehicle mathematical problem formulations for all three VRPPD types are given, and the respective exact, heuristic, and metaheuristic solution methods are discussed.      

Nonlinear effects of exchange rate volatility on the volume of bilateral exports

In this paper, we investigate empirically the impact of exchange rate volatility on real international trade flows utilizing a 13‐country data set of monthly bilateral real exports for 1980–1998. We compute one‐month‐ahead exchange rate volatility from the intra‐monthly variations in the exchange rate to better quantify this latent variable. We find that the effect of exchange rate volatility on trade flows is nonlinear, depending on its interaction with the importing country's volatility of economic activity, and that it varies considerably over the set of country pairs considered. Copyright © 2003 John Wiley & Sons, Ltd.     

Global analysis and economics III: Pareto Optima and price equilibria

Among other things a global version of the fundamental theorem of welfare economics is proved. One starts with a pure exchange economy with fixed total resources where hypotheses of differentiability, convexity, and monotonicity are made on the utility functions. Let ? be the set of price equilibria where the initial allocation coincides with the final one. Then the map which assigns to such a price equilibrium, the corresponding allocation is a diffeomorphism (a complete correspondence) between ? and the set of Pareto Optima.     

Factors of trade in Europe

We analyze how a set of determinants affect trade among European countries over the period 1992–2008. The factors encompass variables from the areas of geography, culture, institutions, infrastructure, and trade direction. Trade is analyzed for four types of goods: primary goods, parts and components, capital goods, and consumer goods. For each type of good we also distinguish its definition in terms of flows, intensive margin, and extensive margin. Methodologically, we first derive country-pair fixed effects over all possible pairs of export–import partners, and in the second stage we relate fixed effects with a set of influential factors. We show (i) the intuitive and varying effects of geographical, cultural, and institutional factors; (ii) the beneficial effects of soft and hard infrastructure; and (iii) the key importance of trade between old and new EU members.     

Finitely additive exchange economies

It is shown that the core and the set of Walras allocations of a non-atomic exchange economy are equal, if the set A of agents is either countable or a continuum, and even if all subsets of A are admitted as coalitions. The set of Walras allocations is shown to be not empty. These results are obtained by use of finitely additive measures defined on the algebra of all subsets of A.     

Existence of equilibria with infinitely many commodities: Banach lattices reconsidered

The purpose of this paper is twofold. The first aim is to present an extension of the results on the existence of Walrasian equilibrium to the infinite dimensional setting. The result depends on two crucial assumptions. These are the compactness of the collection of feasible allocations and the non-emptiness of the interior of the production set. The proof is a direct generalization of Bewley's (1972) proof for the L_∞ case. The second purpose of this paper is to show that the recent result of Mas-Colell (1986) on the existence of equilibrium for exchange economies on Banach lattices can be obtained through an argument based on the result outlined above. That is, exchange economies on Banach lattices with ‘uniformly proper’ preferences behave as though they were production economies in which the production sets have non-empty interior.