Inventory Investment Research Articles

Subsidizing Inventory: A Theory of Trade Credit and Pre-Payment

We propose a simple theory of trade credit and prepayment. A downstream firm trades off inventory holding costs against lost sales. Lost final sales impose a negative externality on the upstream firm. We show that allowing the downstream firm to pay with a delay, an arrangement known as “trade credit,” is precisely the solution to the problem. Solving a reverse externality accounts for the use of prepayment for inputs, even in the absence of any risk of default by the downstream firm. We clarify previously unexplained facts including the universal presence of a zerointerest component in trade credit terms, and the non-responsiveness of interest charges to fluctuations in the bank rate as well as market demand. We explain why trade credit is short term credit and why the level of provision is negatively related to sales and profit and inventory, but positively related to the profit margin. Finally, we show that under trade credit, inventory investment is invariant to the real interest rate for a wide range of parameters, explaining the puzzle posed by Blinder and Maccini (1991). This implies that standard empirical inventory models would gain explanatory power by including the subsidy effect of accounts payable.

Inventories, business cycles, and variable capital utilization

AbstractBils and Kahn [Bils, M., and J. A. Kahn. 2000. “What Inventory Behavior Tells us about Business Cycles.”

Inventory accumulation, location and financial structure: evidence from China

Purpose – The purpose of this paper is to empirically examine the relationship between firms' inventory accumulation and financial structure. It further investigates the impact of geographical locations on firms' inventory investment decision after controlling for firms' financial structure. Design/methodology/approach – This paper uses a large panel of over 1,400 Chinese listed firms that issued. Findings – Firms' financial structure, as reflected in the availability of internal and external capital, has significant impact on firms' inventory decisions. In addition, it is found that firms headquartered in major economic development areas (EDA) tend to have slower inventory growth than firms located in rural areas. Moreover, the results reveal that locating in major EDA facilitates firms' stockpiling of inventories through easy access to external capital. Originality/value – This study not only contributes to the studies on the interactions between firms' location and their financing and investment policy, but also improves our understanding about emerging markets such as China.

A Minimax Distribution Free Procedure for a Multi-constraint Inventory Model with Deterministic Variable Lead Time

Nowadays, considering real environment limitations, the effect of some constraints such as storage space and budget in determining optimal policies of inventory/production systems is a momentous concern of inventory managers. Hence, here, a budget constraint on total inventory investment and a maximum permissible storage space constraint are added simultaneously to a stochastic continuous review inventory system. The piece-wise linear crashing cost function which is widely used in project management is considered in this paper. The study relaxes the assumption about the form of distribution function of lead time demand by only assuming the mean and standard deviation of lead time demand are known. A minimax distribution free procedure is developed for the constrained problem. This study also shows that the respective budget and storage space constrained inventory model to be minimized is jointly convex in the decision variables. A numerical example is given to illustrate the discussed model.

A simulation optimization approach for a two-echelon inventory system with service level constraints

In this paper, we present a simulation optimization algorithm for solving the two-echelon constrained inventory problem. The goal is to determine the optimal setting of stocking levels to minimize the total inventory investment costs while satisfying the expected response time targets for each field depot. The proposed algorithm is more adaptive than ordinary optimization algorithms, and can be applied to any multi-item multi-echelon inventory system, where the cost structure and service level function resemble what we assume. Empirical studies are performed to compare the efficiency of the proposed algorithms with other existing simulation algorithms.

Inventory investment and financial constraints in the Italian manufacturing industry: A panel data GMM approach

Three large unbalanced panels of Italian manufacturing firms observed over the period 1991–2009 are employed to assess, by means of a dynamic GMM approach, whether the existence of financial frictions is suitable to explain deviations of inventories from their long-run path. A negative response of inventory investment to the presence of financial burdens might provide evidence of a significant role played by the financial framework in conditioning the real side of the economy, especially during recession years, when liquidity problems arise. The negative effect is found over the entire analyzed period, with firms' dimensional aspects accounting more than risk characteristics to explain the phenomenon, but the inclusion of recessionary dummies into the model leads to controversial and puzzling results. A significant recessionary effect is found during the Nineties, accounting for inventories being more sensitive to financial frictions during the main recessionary peaks, 1993 and 1996. The result is not confirmed by the most recent estimates, especially the ones referring to the 2008–2009 recessionary shock, whose effects are investigated for the first time by a paper addressing the inventory investment–financial constraints subject. Alternative hypothesis for the proposed results have been tested on data. Firms were found to rely on inventory decumulation to a lesser extent compared to the past, to generate internal financing. More specifically, disinvestments in financial assets were found to represent, as a matter of fact, one of the main drivers adopted to ease liquidity tensions: a negative and strongly significant relationship with inventory investment was detected, after controlling for short-run liquidity constraints at firm level. By contrast, only a weak negative relationship was established with fixed capital during the same recessionary biennium.

Net present value analysis of the economic production quantity

Using Laplace transforms we extend the economic production quantity (EPQ) model by analysing cash flows from a net present value (NPV) viewpoint. We obtain an exact expression for the present value of the cash flows in the EPQ problem. From this, we are able to derive the optimal batch size. We obtain insights into the monotonicity and convexity of the present value of each of the cash flows, and show that there is a unique minimum in the present value of the sum of the cash flows in the extended EPQ model. We also obtain exact point solutions at several values in the parameter space. We compare the exact solution to a Maclaurin series expansion and show that serious errors exist with the first-order approximation when the production rate is close to the demand rate. Finally, we consider an alternative formulation of the EPQ model when the opportunity cost of the inventory investment is made explicit.

Lead Time Reduction in Budget and Storage Space Restricted Lot Size Reorder Point Inventory Models with Controllable Negative Exponential Backorder Rate

This study presents the mixed backorder and lost sales inventory models involving four variables; order quantity, lead time, safety factor (a discrete variable) and backorder rate. A controllable negative exponential backorder rate is considered in the proposed model. In the real market, as unsatisfied demands occur, the longer length of lead time is, the smaller proportion of backorder rate would be. Considering this reason, backorder rate is dependent on the length of lead time through the amount of shortages. The negative exponential lead time crashing cost is considered in this study. Today, the cost of land acquisition is high in most of the countries and one of the main concerns of inventory managers is to ensure that the maximum permissible storage space is enough when an order arrives. Hence, a random storage space constraint is considered, since, the inventory level is random when an order arrives. So, in this case, a chance-constrained programming technique is used to make it crisp. Moreover, another significant concern of inventory managers is how to control the maximum investment in the inventory. This study assumes the purchasing cost is paid at the time of order placing. Considering this assumption, a budget constraint is also added to the model in order to managing the maximum inventory investment. The lead time demand, first, follows a normal distribution and then, relaxes the distribution function assumption by only assuming the mean and variance of lead time demand are known and applies the minimax distribution free procedure to solve the problem. Furthermore, a numerical example is also given to illustrate the models and solution procedures.

Design of inventory pools in spare part support operation systems

The objective of a spare part support operation is to fulfill the part request order with different service contracts in the agreed response time. With this objective to achieve different service targets for multiple service contracts and the considerations of inventory investment, it is not only important to determine the inventory policy but also to design the structure of inventory pools and the order fulfilment strategies. In this research, we focused on two types of inventory pools: multiple inventory pool (MIP) and consolidated inventory pool (CIP). The idea of MIP is to maintain separated inventory pools based on the types of service contract, while CIP solely maintains a single inventory pool regardless of service contract. Our research aims to design the inventory pool analytically and propose reserve strategies to manage the order fulfilment risks in CIP. Mathematical models and simulation experiments would be applied for analysis and evaluation.

Inventory Investment and the Empirical Phillips Curve

In this paper, we study the Calvo pricing models with finished goods inventory investment to demonstrate that the current inflation can be expressed as a function of the marginal cost of sales, not the marginal production cost, and expected future inflation. Under the assumption that the true aggregate marginal costs are not observable in actual data, we make use of equilibrium conditions for aggregate finished goods inventories to measure the time series of marginal costs, thereby leading to the construction of inflation series on the basis of the Phillips curve. Our results indicate the possibility of a successful fit of the empirical New Keynesian Phillips curve without relying on unit labor cost—a conventional measure of marginal production cost in the literature.

Inventory investment and the business cycle: the usual suspect

From quarterly postwar US and French data, this paper provides evidence of a bounce-back effect in inventory investment but not in final sales data. Actually, from a bounce-back augmented threshold model, it appears that i) the null hypothesis of no bounce-back effect is strongly rejected by the inventory investment data and ii) the one-step ahead forecasting performances of the models accounting for this bounce-back effect are well improved compared to linear or standard threshold autoregressions. This supports the conventional wisdom that inventory investment exacerbates aggregate fluctuations, in line with the recent theoretical models by, e.g., Wang and Wen (Wang, P., and Y. Wen. 2009. Inventory Accelerator in General Equilibrium. Working Paper 010, Federal Reserve Bank of St. Louis) and Wang, Wen and Xu (Wang, P., Y. Wen, and Z. Xu. 2011. When do Inventories Destabilize the Economy? An Analytical Approach to (s,s) Policies. Working Paper 014, Federal Reserve Bank of St. Louis) which clearly predict a destabilizing role of inventory investment over the business cycle. By contrast, our empirical findings cast doubt on models based on the stockouts avoidance motive for holding inventories.

Tradeoff Analysis for Optimal Multiobjective Inventory Model

Deterministic inventory model, the economic order quantity (EOQ), reveals that carrying inventory or ordering frequency follows a relation of tradeoff. For probabilistic demand, the tradeoff surface among annual order, expected inventory and shortage are useful because they quantify what the firm must pay in terms of ordering workload and inventory investment to meet the customer service desired. Based on a triobjective inventory model, this paper employs the successive approximation to obtain efficient control policies outlining tradeoffs among conflicting objectives. The nondominated solutions obtained by successive approximation are further used to plot a 3D scatterplot for exploring the relationships between objectives. Visualization of the tradeoffs displayed by the scatterplots justifies the computation effort done in the experiment, although several iterations needed to reach a nondominated solution make the solution procedure lengthy and tedious. Information elicited from the inverse relationships may help managers make deliberate inventory decisions. For the future work, developing an efficient and effective solution procedure for tradeoff analysis in multiobjective inventory management seems imperative.

Do Wild Fluctuations in Quarterly Inventory Investment Data Matter?:

Do Wild Fluctuations in Quarterly Inventory Investment Data Matter?:

On establishing initial inventory levels in the rent-to-own industry: an empirical analysis

A theoretic model is developed to calculate the optimal inventory investment for a firm in the rent-to-own industry. This investment question is shown to be equivalent to a queueing problem and queueing technology is employed to fashion a solution. The initial inventory level is a critical decision which should be made to maximise expected profit. The decision is complicated by the fact that the arrival process of new customers, the total number of times that an item will be rented, and the length of time an item is kept by a customer are all random variables. Despite this, the model is able to provide closed-form solutions for various parameters, e.g., the probability that a potential customer will be lost due to product unavailability. A compelling feature of the current study is our access to a large and detailed transactional database. This is used to gain insight into actual contract usage and to numerically estimate the input parameters to our model. The resultant optimal inventory level is then compared against the actual levels providing a clear goodness-of-fit test for our overall approach.

A possibilistic multiple objective pricing and lot-sizing model with multiple demand classes

We address an inventory-marketing system to determine the production lot size, marketing expenditure and selling prices where a firm faces demand from two or more market segments in which the firm can set different prices. Considering pricing, marketing and lot-sizing decisions simultaneously, the model maximizes the profit and return on inventory investment under multiple time varying demand classes. The model is formulated as a fuzzy non-linear multi-objective one where some parameters are ill-known and modeled by fuzzy numbers. A hybrid possibilistic-flexible programming approach is proposed to handle imprecise data and soft constraints concurrently. After transforming the original model into an equivalent multi-objective crisp model, it is then converted to a classical mono-objective one by a fuzzy goal programming method. An efficient solution procedure using particle swarm optimization (PSO) is also provided to solve the resulting non-linear problem.

The Inventory Growth Spread

Previous studies show that firms with low inventory growth outperform firms with high inventory growth in the cross-section of publicly traded firms. In addition, inventory investment is volatile and procyclical, and inventory-to-sales is persistent and countercyclical. We embed an inventory holding motive into the investment-based asset pricing framework by modeling inventory as a factor of production with convex and nonconvex adjustment costs. The augmented model simultaneously matches the large inventory growth spread in the data, as well as the time-series properties of the firm level capital investment, inventory investment, and inventory-to-sales. Our conditional single-factor model also implies that traditional unconditional factor models such as the CAPM should fail to explain the inventory growth spread, although not with the same large pricing errors observed in the data.

New Orders and Asset Prices

This paper investigates the behavior of the ratio of new orders to shipments of durable goods (NO/S). High levels of NO/S are associated with a business cycle peak. They predict a short-run increase in employment and fixed and inventory investment but a dramatic long-run decline in employment, fixed investment, inventories, and GDP as a whole. We also find that NO/S captures time-varying risk premia. Higher levels of NO/S forecast lower excess returns on a broad set of assets, including equities, longand intermediate-term Treasury bonds, and high- and low-grade corporate bonds, at horizons from one month to one year. These effects are robust to the inclusion of all common return predictors. We then construct an equilibrium model of investment with time to plan and a countercyclical price of risk which implies that the ratio of new orders to shipments is procyclical and predicts lower excess returns.

Inventory Investment Dynamics and Recoveries: A Comparison of Manufacturing and Retail Trade Sectors

This paper explores the existence of a bounce-back effect in inventory investment using the European Commission opinion survey on stocks of finished products in manufacturing and retail trade sectors. The data are quarterly balance for France, Germany and a European aggregate, from 1985q1 to 2011q4. Our empirical findings support the existence of a high recovery episode for inventory investment, during the quarters immediately following the recessions. This could in turn explain the real GDP growth rate bounce-back pointed out in previous empirical studies. Moreover, according to our estimates, the inventory investment bounce-back occurs later and lasts longer in manufacturing than in retail trade sector.

Inventory investment and the cost of capital

We examine the relation between inventory investment and the cost of capital in the time series and the cross section. We find consistent evidence that risk premiums, rather than real interest rates, are strongly negatively related to future inventory growth at the aggregate, industry, and firm levels. The effect is stronger for firms in industries that produce durables rather than nondurables, exhibit greater cyclicality in sales, require longer lead times, and are subject to more technological innovation. We then construct a production-based asset pricing model with two types of capital, fixed capital and inventories, to explain these empirical findings. Convex adjustment costs and a countercyclical price of risk lead to negative time series and cross-sectional relations between expected returns and inventory growth.

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