On the smoothness of optimal paths

Abstract The aim of this paper is to study the differentiability property of optimal paths in dynamic economic models. We address this problem from the point of view of the differential calculus in sequence spaces which are infinite-dimensional Banach spaces. We assume that the return or utility function is concave, and that optimal paths are interior and bounded. We study the C ^r differentiability of optimal paths vis-à-vis different parameters. These parameters are: the initial vector of capital stock, the discount rate and a parameter which lies in a Banach space (which could be the utility function itself). The method consists of applying an implicit function theorem on the Euler–Lagrange equation. In order to do this, we make use of classical conditions (i.e., the dominant diagonal block assumption) and we provide new ones. Mathematics Subject Classification (2000): 90A16, 49K40, 93C55 Journal of Economic Literature Classification: C161, D99, O41     

Aggregate Matching Efficiency: A Stochastic Production Frontier Approach, France 1990–1994

We evaluate the determinants of aggregate matching efficiencychanges through a stochastic translog production frontiermodel. The efficiency coefficient is represented by a stochasticfunction of variables meant to capture workers and firmscharacteristics. The model is estimated on French data coveringtwenty-two regions from March 1990 till February 1995. Ourestimates suggest that aggregate matching efficiency has decreasedsteadily in the early nineties. There are also wide cross-regionaldifferences. On average, about 30% of the variations ofefficiency observed across time and regions can be related tochanges in the explanatory variables used in the model. The mostimportant explanatory variables are the proportion of youngsters,females and immigrants in the stock of job seekers. Long-termunemployment has a significant negative effect, population densitya significant positive one. The huge decline in the proportion ofpermanent job offers has apparently little effect on matchingefficiency.     

Optimal Pricing and Price-Cap Regulation in the Postal Sector

This paper studies the optimal price structure in the postal sector when worksharing is available (e.g., for collection, sorting and transportation) and when the operator faces a break-even constraint. Users differ in opportunity and cost to engage in worksharing. We determine the optimal worksharing discount and provide sufficient conditions (on demand functions) under which it exceeds the ECPR level. Furthermore, we show that the optimal prices can be implemented through a global price cap imposed on a weighted average of the prices of all products. The appropriate weights are proportional to the market demand (evaluated at optimal prices) of the corresponding products.     

Barriers to knowledge spillovers and regional convergence in an evolutionary model

This paper will present a multi-region/multi-country model in which inter-regional knowledge spillovers determine the growth of regions. Key parameters in the model are the learning capability of a region and the rate of knowledge generation (R&D). The intensity of spillovers depends on geographical distance between regions. The model is investigated by means of simulation techniques. What results is a core-periphery situation, the exact form of which depends on the assumed spatial structure. The impact of economic integration is investigated by introducing barriers-to-knowledge-spillovers in the model in the form of borders between countries. Contrary to the popular belief and some economic theories, we find that removing such spillover barriers may result in larger disparity of income levels between regions.     

Partner selection and governance design in interfirm relationships

This paper develops a structural model to simultaneously analyze firms’ partner selection activities and governance design for managing interfirm relationships. The model predicts these choices to be influenced by appropriation concerns, coordination requirements, dependence and prior experiences with the exchange partner. An analysis of 817 information technology transactions shows that appropriation concerns, coordination requirements and dependence influence governance design, while buyers’ partner selection effort relates mainly to appropriation concerns. Partner experience developed during prior ties with the exchange partner is found to moderate the effects of these control problems. In addition, partner selection and formal governance are found to be used as complements instead of substitutes in coping with interfirm control problems.     

Product Innovation Processes in Small Firms: Combining Entrepreneurial Effectuation and Managerial Causation

This article reports a multimethod study of product innovation processes in small manufacturing firms. Prior studies found that small firms do not deploy the formalized processes identified as best practice for the management of new product development (NPD) in large firms. To explicate small firms' product innovation, this study uses effectuation theory, which emerged from entrepreneurship research. Effectuation theory discerns two logics of decision‐making: causation, assuming that means are selected to attain goals; and effectuation, assuming that goals are created based upon available means. The study used a process research approach, investigating product innovation trajectories in five small firms across 352 total events. Quantitative analyses revealed early effectuation logic, which increasingly turned toward causation logic over time. Further qualitative analyses confirmed the use of both logics, with effectual logic rendering product innovation resource‐driven, stepwise, and open‐ended, and with causal logic used especially in later stages to set objectives and to plan activities and invest resources to attain objectives. Because the application of effectuation logic differentiates the small firm approaches from mainstream NPD best practices, this study examined how small firms' product innovation processes deployed effectuation logic in further detail. The small firms: (1) made creative use of existing resources; (2) scoped innovations to be realizable with available resources; (3) used external resources whenever and wherever these became available; (4) prioritized existing business over product innovation projects; (5) used loose project planning; (6) worked in steps toward tangible outcomes; (7) iterated the generation, selection, and modification of goals and ideas; and (8) relied on their own customer knowledge and market probing, rather than early market research. Using effectuation theory thus helps us understand how small firm product innovation both resembles and differs from NPD best practices observed in larger firms. Because the combination of effectual and causal principles leverages small firm characteristics and resources, this article concludes that product innovation research should more explicitly differentiate between firms of different sizes, rather than prescribing large firm best practices to small firms.     

The Impact of Introducing Insurance Guaranty Schemes on Pricing and Capital Structure

The introduction of an insurance guaranty scheme can have significant influence on the pricing and capital structures in a competitive market. The aim of this article is to study this effect on competitive equity–premium combinations while considering a framework with policyholders and equity holders where guaranty fund charges are volume‐based, as levied in existing schemes. Several settings with regard to the origin of the fund contributions are assessed and the immediate effects on the incentives of the policyholders and equity holders are analyzed through a one‐period contingent claim approach. One result is that introducing a guaranty scheme in a market with competitive conditions entails a shift of equity capital towards minimum solvency requirements. Hence, adverse incentives may arise with regard to the overall security level of the industry.     

DYNAMIC HEDGE FUND STYLE ANALYSIS WITH ERRORS‐IN‐VARIABLES

We revisit the traditional return‐based style analysis in the presence of time‐varying exposures and errors‐in‐variables (EIV). We apply a benchmark selection algorithm using the Kalman filter and compute the estimated EIV of the selected benchmarks. We adjust them by subtracting their EIV from the initial return series to obtain an estimate of the true uncontaminated benchmarks. Finally, we run the Kalman filter on these adjusted regressors. Analyzing EDHEC alternative index styles, we show that this technique improves the factor loadings and allows more precise identification of the return sources of the considered hedge fund strategy.     

Travel and activity time allocation: An empirical comparison between eight cities in Europe

A study of daily time allocation to travel and out-of-home activity is conducted across eight European cities over three countries: France (Lyon, Grenoble, Strasbourg and Rennes), Switzerland (Geneva, Bern and Zurich) and Belgium (Brussels), based on individual travel survey data collected between 1997 and 2006. The effects of socio-demographic, spatial context, transport availability and city-specific variables are investigated thanks to the Cox proportional hazard model. The results indicate that socio-demographic characteristics and city (or country) specific effect play a major role while residential density and proximity to high level road or public transport networks have a very limited impact on time budgets for travel and out-of-home activities.     

EXPLAINING RISING INEQUALITY: SKILL‐BIASED TECHNICAL CHANGE AND NORTH–SOUTH TRADE*

Abstract We review the ‘skill‐biased technological change (SBTC) versus North–South trade (NST)’ debate in order to explain widening wage inequality between skilled and unskilled workers. The traditional explanations based on exogenous SBTC and on the North–South Heckscher–Ohlin–Samuelson approach, as well as the early estimates that diagnosed a clear prevalence of the former, are firstly exposed and discussed. A presentation is then made of the recent theoretical literature that endogenizes SBTC, introduces new channels of impacts from NST, and combines both explanations. Finally, the current estimates show that (i) both explanations are relevant, (ii) their impacts differ according to industries and countries, (iii) outsourcing is the main vector of impact from NST and (iv) SBTC and NST interact.