Common inventory modeling assumptions that fall short: Arborescent networks, Poisson demand, and single-echelon approximations

Traditional multi-echelon inventory theory focuses on arborescent supply chains that use a central warehouse which replenishes remote warehouses. The remote warehouses serve customers in their respective regions. Common assumptions in the academic literature include use of the Poisson demand process and instantaneous unit-by-unit replenishment. In the practitioner literature, single-echelon approximations are advised for setting safety stock to deal with lead time, demand, and supply variations in these settings. Using data from a U.S. supplier of home improvement products, we find that neither the assumptions from the academic literature nor the approximations from the practitioner literature necessarily work well in practice.In a variation of the strictly arborescent supply chain, the central warehouse at our real company not only replenishes other warehouses but also meets demand from customers in the region near the central warehouse. In this paper, we study this dual-role central warehouse structure, which we believe is common in practice. Using high and low volume product demand data from this company, we use Monte Carlo simulations to study the impact of (1) the use of a dual-role centralized warehouse, (2) common demand assumptions made in multi-echelon research, and (3) single-echelon approximations for managing a multi-echelon supply chain. We explore each of these under both centralized and decentralized control logic. We find that the common assumptions of theoretical models impede their usefulness and that heuristics that ignore the actual supply chain structure fail to account for additional opportunities to utilize safety stock more effectively. Researchers should be aware of the gap between standard assumptions in traditional literature and actual practice, and critically evaluate their assumptions to find a reasonable balance between tractability and relevance.     

Labor supply and the optimality of Social Security

Traditional economic theory predicts that an unfunded public pension system can be justified on the basis of its ability to provide intergenerational transfers, and also for its ability to provide partial insurance against mortality and labor income risks. In this paper, I demonstrate that the quantitative importance of these traditional roles depends on how the pension system distorts households' labor supply decisions. Using a general-equilibrium life-cycle consumption model calibrated to the U.S. economy, I show that these distortions can be large enough to erase much of the traditional welfare gains from Social Security. I also find that this fact is robust within the range of labor supply elasticities usually encountered in the macroeconomic literature.     

The role of health insurance in labor supply decisions of divorced females

Labor economics literature provides evidence that marital dissolution induces an increase in labor supply of females. This paper explores an explanation for this finding: Marital separation might place wives at risk of losing health insurance or increase the need for expanded health coverage. Thus, wives must increase their labor supply in order to qualify for health benefits. Using data from the National Longitudinal Survey of Youth, results confirm that marital dissolution is associated with increased female labor supply. However, this effect is mostly concentrated among women who were not previously enrolled in their husbands’ health insurance plans. For wives who were dependent on their husbands for coverage, continuing coverage laws appear to mitigate the effect of marital dissolution on female labor supply.     

The Taylor principle fights back,Part II

The existing literature holds that the Taylor principle often leads to indeterminacy in New Keynesian models that allow for capital accumulation and limited asset market participation. This conclusion is special, however, to the case of continuous full employment. When the assumption of perfect wage flexibility is relaxed very slightly so that the labor market clears quickly but not instantaneously, determinacy is the norm. The threat of indeterminacy is limited to a tiny, irrelevant corner of the parameter space where the elasticity of labor supply is unusually high and real wage adjustment is unbelievably fast. Everywhere else, the Taylor principle guarantees a unique rational expectations equilibrium. The dramatic difference in results reflects the sensitivity of the monetary transmission mechanism to the speed of adjustment in the labor market.     

THEORETICAL AND PRACTICAL ARGUMENTS FOR MODELING LABOR SUPPLY AS A CHOICE AMONG LATENT JOBS

Models of labor supply derived from stochastic utility representations and discretized sets of feasible hours of work have gained popularity because they are more practical than the standard approaches based on marginal calculus. In this paper we argue that practicality is not the only feature that can be addressed by means of stochastic choice theory. This theory also offers a powerful framework for developing a more realistic model for labor supply choices, founded on individuals having preferences over jobs and facing restrictions on the choice of jobs and hours of work. We discuss and clarify how this modeling framework deviates from both the conventional discrete approach [Van Soest, A. ( 1995 ) Structural models of family labor supply. A discrete choice approach. Journal of Human Resources 30: 63–88), as well as the standard textbook approach based on marginal calculus (Hausman, J.A. ( 1992 ) The econometrics of nonlinear budget sets. Econometrica 53: 1255–1282]. We furthermore discuss how the model based on job choice can be applied to simulate effects of alternative restrictions on hours of work.     

A simultaneous model for regional labor supply, incorporating labor force participation, commuting and migration

Simultaneous relations between various components of the regional supply of labor and the situation on the regional labor market are developed. There is a distinction between migration, participation and commuting. Conventional research only devotes attention towards the partial relation between one of these components and the regional labor market situation. However, many decisions people make, involve a simultaneous approach towards participation, commuting and migration. This approach is operationalized at a macro-level by constructing a simultaneous supply model. For the specifications we go back to standard literature. In each of the equations, apart from variables that are specific for the particular function, special attention is given to the interrelation between the three supply variables. An overall simultaneity is described by a fourth endogenous variable: unemployment; this variable is explained by employment, participation, netmigration and netcommuting. A combined time-series/cross-section-analysis is used to estimate the model.

Surprisingly it appears that in comparison with OLS parameter- and t-values of the supply-equations are not affected by the use of simultaneous estimation techniques. Only for the unemployment-equation there are significant changes.     

Considering grievance mediation

This article uses a public sector case study and a review of the social science literature on disputing processes to question assumptions made by labor relations advocates of grievance mediation. The author argues that labor policy on alternative grievance resolution processes cannot be adequately made without consideration of the specific labor-management relationship within its social context. A model is proposed to assist parties considering grievance mediation by making the social context more explicit.     

A Multi-state model of state dependence in labor supply: Intertemporal labor supply effects of a shift from joint to individual taxation

In this paper I develop an intertemporal discrete choice model of female labor supply to analyze the effects of true state dependence and its effect on labor supply behavior over time. The estimation results show that state dependence is significantly positive at the extensive margin and lower but in general still significant at the intensive margin. I apply this model to study the short and long run labor supply effects of a fundamental reform of the German income tax system, i.e. the shift from joint to individual taxation of married couples and show that labor supply responses are significantly higher in the long run than in the short run.     

The effect of labor supply changes on output: empirical evidence from US industries

In this paper we examine the relationship between labor supply and industry-level output in the context of the specific factors model. Jones (Trade, balance of payment and growth: essays in honor of Charles P. Kindleberger, Amsterdam, pp 3–21, 1971) shows that a rise in the amount of labor in the economy will increase the output in all industries. We empirically show which industry output is predicted to expand more when the size of labor force grows. Unlike the commonly used Rybczynski Theorem (Economica 22:336–341, 1955) of the Heckscher-Ohlin model, the specific factors model shows that a comparison both of labor intensities and labor demand elasticities plays an important role in determining which output expands relatively more when the size of labor force grows. For this purpose, we illustrate the importance of the parameters of the model in determining how changes in the labor supply affect the output change, with special reference to elasticities of substitution in production. We estimate the elasticity of substitution by using CES production function and show how these estimates describe the general equilibrium of production with one mobile factor (labor) and 25 industries of the US economy using data for 1979–2001. We show that the increase in the supply of labor raise output in all industries, but the magnitudes of the increases in some industries are more than others depending on the value of the elasticity of substitution along with factor intensities between industries. The largest output effect occurs for educational, health care and social service, where a 1 % supply of labor increase would raise output 10.5 %. However, the growth in the labor supply has a small impact on output growth in the range of 0.1–0.6 % in agriculture, petroleum, coal product and finance and insurance industries.     

Retirement and social security: the roles of self-fulfilling expectations and educational investments

Countries with higher implicit taxes on continued work are associated with lower labor force participation rates of the elderly. This paper constructs a politico-economic model that accounts for this feature based on multiple, self-fulfilling expectations of agents. In this model, agents are identical at birth and can become skilled (or remain unskilled) through educational investment. When agents hold expectations of larger social security benefits, it provides a disincentive to engage in educational investment, thereby resulting in an unskilled majority. In turn, this unskilled majority supports larger social security benefits, which induces the retirement of the elderly and thus results in a lower labor force participation rate. The opposite applies when agents have expectations of smaller social security benefits in their old age.     

Empirical labor search: A survey

This paper surveys the existing empirical research that uses search theory to empirically analyze labor supply questions in a structural framework, using data on individual labor market transitions and durations, wages, and individual characteristics. The starting points of the literature are the Mincerian earnings function, Heckman's classic selection model, and dynamic optimization theory. We develop a general framework for the labor market where the search for a job involves dynamic decision making under uncertainty. It can be specialized to be in agreement with most published research using labor search models. We discuss estimation, policy evaluation with the estimated model, equilibrium model versions, and the decomposition of wage variation into factors due to heterogeneity of various model determinants as well as search frictions themselves. We summarize the main empirical conclusions.     

Sustainable evaluation and verification in supply chains: Aligning and leveraging accountability to stakeholders

Managers are being challenged by multiple (and diverse) stakeholders, which have variety of expectations and informational needs about their firm’s supply chains. Collectively, these expectations and needs form a multi-faceted view of stakeholder accountability, namely the extent to which a firm justifies behaviors and actions across its extended supply chain to stakeholders. To date, sustainable supply chain management research has largely focused on monitoring as a self-managed set of narrowly defined evaluative activities employed by firms to provide stakeholder accountability. Nevertheless, evidence is emerging that firms have developed a wide variety of monitoring systems in order to align with stakeholders’ expectations and leverage accountability to stakeholders. Drawing from the accounting literature, we synthesize a model that proposes how firms might address accountability for sustainability issues in their supply chain. At its core, the construct of sustainable evaluation and verification (SEV) captures three interrelated dimensions: inclusivity, scope, and disclosure. These dimensions characterize how supply chain processes might identify key measures, collect and process data, and finally, verify materiality, reliability and accuracy of any data and resulting information. As a result, the concept of monitoring is significantly extended, while also considering how different stakeholders can play diverse, active roles as metrics are established, audits are conducted, and information is validated. Also, several antecedents of SEV systems are explored. Finally, the means by which an SEV system can create a competitive advantage are investigated.     

CHILD CARE PRICES AND MATERNAL EMPLOYMENT: A META‐ANALYSIS

The literature estimates for labor force participation elasticity with regard to child care prices are extensive and varying. While some estimates imply substantial gains from child care subsidies, others find insignificant effects. To determine the causes of the variance, this paper reviews and analyzes the elasticity sizes using estimates from 36 peer‐reviewed articles and working papers in the literature. We start by reviewing the theoretical and empirical aspects related to participation elasticity with regard to child care costs, paying special attention to sample characteristics, methodological aspects, and macro level factors. We conclude by providing a meta‐regression using control variables based on our review of the literature to explain some of the differences between the estimates. As research builds on and improves the methods and assumptions in prior works, elasticity estimates have become smaller over time. This decline might also be partially explained by changes in labor market characteristics. In countries with high rates of part‐time work and very high or very low rates of female labor force participation, we find elasticity rates to be smaller.     

Testing the intertemporal labor supply model: are jobs important?

The neoclassical life-cycle labor supply model assumes that hours of work are determined by labor supply choices alone and does not include a role for employers or job distinctions. An alternative model in which employers have an interest in employee hours and changing jobs is costly may reconcile weak and conflicting evidence regarding the neoclassical model. An important implication of such an alternative is that individuals may face hours constraints on a job and thus can choose hours freely only between jobs. This paper tests several implications of the neoclassical model against this alternative model of hours determination. Using a unique panel of individuals and jobs constructed using data on women from the 1988–1992 Panel Study of Income Dynamics, I compare hours variances and labor supply elasticities measured within and between jobs. Results provide some evidence against the neoclassical model and suggest that ignoring the role of employers in determining hours of work can lead to downward bias in estimates of labor supply elasticities.     

Inter-city wage differentials and the value of air quality

This paper proposes a method of valuing air quality based on differences in wages among cities. Using an urban location model it is shown that the supply of labor to any city increases with the real wage and with air quality in the business district. If individuals have log-linear utility functions then the value at home and at work of an equal proportionate reduction in pollution throughout the city can be computed from the coefficients of the labor supply function. The computations are illustrated for one-digit labor supply functions estimated from 1970 Census data.     

Urban disamenities and the measure of economic welfare

A labor market model is used to estimate elasticities between various disamenity factors of urban areas and the wage in those areas. The results are used to calculate a correction to the personal income (PI) data for use in the construction of an index to be used as a measure of economic welfare. The labor supply equation of the model includes some population-related variables which Tobin and Nordhaus have hypothesized represent disamenities of urban living. The labor demand equation is derived from a production function which includes a measure of agglomeration economies. A two-stage least-squares regression analysis provides results which indicate that the hypothesized factors are actually amenity factors. The resulting correction to the personal income data is thus an addition: Economic welfare is higher than that indicated by the PI statistics.     

Stochastic non-smooth envelopment of data: semi-parametric frontier estimation subject to shape constraints

The field of productive efficiency analysis is currently divided between two main paradigms: the deterministic, nonparametric Data Envelopment Analysis (DEA) and the parametric Stochastic Frontier Analysis (SFA). This paper examines an encompassing semiparametric frontier model that combines the DEA-type nonparametric frontier, which satisfies monotonicity and concavity, with the SFA-style stochastic homoskedastic composite error term. To estimate this model, a new two-stage method is proposed, referred to as Stochastic Non-smooth Envelopment of Data (StoNED). The first stage of the StoNED method applies convex nonparametric least squares (CNLS) to estimate the shape of the frontier without any assumptions about its functional form or smoothness. In the second stage, the conditional expectations of inefficiency are estimated based on the CNLS residuals, using the method of moments or pseudolikelihood techniques. Although in a cross-sectional setting distinguishing inefficiency from noise in general requires distributional assumptions, we also show how these can be relaxed in our approach if panel data are available. Performance of the StoNED method is examined using Monte Carlo simulations.     

Response to updated mortality forecasts in life cycle saving and labor supply

Historical evidence shows that demographic forecasts, including mortality forecasts, have often been grossly in error. One consequence of this is that forecasts are updated frequently. How should individuals or institutions react to updates, given that these are likewise expected to be uncertain? We discuss this problem in the context of a life cycle saving and labor supply problem, in which a cohort of workers decides how much to work and how much to save for mutual pensions. Mortality is stochastic and point forecasts are updated regularly. A Markovian approximation for the predictive distribution of mortality is derived. This renders the model computationally tractable, and allows us to compare a theoretically optimal rational expectations solution to a strategy in which the cohort merely updates the life cycle plan to match each updated mortality forecast. The implications of the analyses for overlapping generations modeling of pension systems are pointed out.     

Consumption and labor supply

We present a new econometric model of aggregate demand and labor supply for the United States. We also analyze the allocation full wealth among time periods for households distinguished by a variety of demographic characteristics. The model is estimated using micro-level data from the Consumer Expenditure Surveys supplemented with price information obtained from the Consumer Price Index. An important feature of our approach is that aggregate demands and labor supply can be represented in closed form while accounting for the substantial heterogeneity in behavior that is found in household-level data. As a result, we are able to explain the patterns of aggregate demand and labor supply in the data despite using a parametrically parsimonious specification.     

Anticipation,learning and welfare: the case of distortionary taxation

We study the impact of anticipated fiscal policy changes in a Ramsey economy where agents form long-horizon expectations using adaptive learning. We extend the existing framework by introducing distortionary taxes as well as elastic labor supply, which makes agents’ decisions non-predetermined but more realistic. We detect that the dynamic responses to anticipated tax changes under learning have oscillatory behavior that can be interpreted as self-fulfilling waves of optimism and pessimism emerging from systematic forecast errors. Moreover, we demonstrate that these waves can have important implications for the welfare consequences of fiscal reforms.