SUMMARY

The objective of the research is to design a procedure for inventory management in trading entities with independent demand. The procedure presents an economically argued analysis to establish inventory levels that report a lower cost and provide improvements that contribute to the improvement of supply management. The methodological contribution of this research is given by the integration of commercial and economic management, the analysis of the economic feasibility of establishing inventory levels, in addition to the application of diagnostic indicators and criteria for a better selection of forecasting techniques. of the products. Theoretical methods were used: analysis-synthesis, inductive-deductive and analytical-synthetic; and empirical like surveys,interviews and document review.

The proposal represents an optimization of transport and storage management within the logistics network, reporting savings in fuel costs and better use of storage capacities.

Keywords: inventory management, economic analysis, cost of breaking stock, supply management, logistics.

ABSTRACT

The objective of investigation is to design a procedure for the step of inventory at entities marketers with independent request. The procedure presents an analysis economically argumented to establish levels of inventory that they report a minor cost and offering improvements that contribute to the perfecting of the step of provisioning. The methodological contribution of this investigation is given for the integration of the commercial and cost-reducing step, the analysis of the cost-reducing feasibility to establish the levels of inventory, in addition to the application of indicators of diagnosis and criteria for a best choice of the techniques of prognosis of the products. Himself used theoretic methods analysis synthesis, the inductive deductive and the analytical synthetic; And empiricists like opinion polls,interviews and the revision of documents.

The proposal represents an optimization of the transporting negotiations and storage within the logistic net, yielding savings in expenses of fuel and better use of storage capacities.

Key words: Step of inventory, economic analysis, cost of rupture of stock, step of provisioning, logistics.

INTRODUCTION

There is a great diversity of trading companies that generate considerable income for the Cuban national economy. All of them have the same purpose: to consolidate the demand for goods, buying from manufacturers and distributing the product to the end customer, with the application of a certain profit margin to the sale made.

The current situation in Cuba makes it necessary to have storage strategies, thus there is a general tendency to pay close attention to everything related to the supply activity.

Currently, inventory management in trading companies has problems with planning purchases, high inventory costs and non-compliance with the level of service in terms of shortages of products to the population. Other problems are due to the unreliability of the supplier's deliveries, specifically the delay in delivery times and non-compliance with the requested quantities, as well as the low technical availability of transport to distribute in the territory. Other reasons that motivated the present study was the request by the management to know the optimal inventory levels that would guarantee the satisfaction of the assistance to the population, cost efficiency and effectiveness in the process.

In the bibliographic search of procedures or methodologies, exact information was not found that responds to the solution in the determination of inventory levels in marketers, oriented to the external client and to economic efficiency, based on the level of stock and its costs. The above allowed defining as a scientific problem of this research: How to manage within the supply logistics process of a marketing entity with independent demand, reliable inventory levels and with the lowest reporting of costs?

The general objective is: to design a procedure for the inventory management system that guarantees greater inventory reliability and lower costs.

Specific objectives were defined as: to consult updated national and international literature on the subject to determine the state of the art and practice on the subject, to design a procedure that allows analyzing the level of service and inventory management of the organization.

In the development of this research, the following methods were used: synthetic analysis, induction and deduction, surveys, interviews, scientific observation and statistics such as a descriptive measure of trend, exponential smoothing method, inventory model for the periodic review system, among others.. The procedure is essentially characterized by determining the level of inventory aimed at satisfying the external customer from an economic equilibrium point between inventory costs.

DEVELOPING

The proposed procedure is essentially characterized by determining the inventory levels of the products of independent demand, based on the economic analysis of the inventory costs. It proposes a better management of the provisioning subsystem from the solution of problems detected in the diagnosis. It is structured in four stages and includes the tasks associated with each one, defining the techniques and methods to be used.

Stage 1: Engagement and characterization

To carry out studies in any organization, it is of great importance the understanding, on the part of its personnel, of the proposal to improve the change and their commitment to help, as well as the characterization of the organization for a better study.

1. Characterization of the object of study
   • Profile of the organization: Brief historical review, geographical location , corporate purpose, mission and vision Main customers, suppliers and competitors Main characteristics of its human resources and organizational structure.

1. Characterization of the procurement process

• Input and output elements Identification of the information and material flows that make up the supply process: description, interrelation and executor System or control mechanism.

Stage 2: Diagnosis

In this phase, the efficiency and effectiveness of the entity's commercial and procurement processes are evaluated, as well as the detection and verification of the causes that have repercussions as possible restrictions on successful performance.

1. Evaluation of the strategic objectives and the level of service provided

Make the selection of the strategic objectives for the period related to commercial management and the procurement process.

1. Analysis of the economic indicators of the entity under study

It will be done through the analysis of the indicators: Net Profit, Solvency, Liquidity and Inventory Turnover, taking into account its trend and the deviations obtained with respect to the plan.

In order to demonstrate the need for the study and relevance of the deficiencies raised in the problem situation, it is proposed to analyze the Cost of immobilization of the merchandise, Average inventory cost of merchandise and its percentages with respect to the value it represents in sales. The analysis of the Unsatisfied Demand Index indicators (Cost of stock breakdown) and the percentage it represents with respect to the sale is proposed.

1. Service level assessment in inventory management

5.1 Assessment of the level of service provided: service indicators

It is carried out through the analysis of the level of assurance of inventories in terms of compliance in deliveries according to term, assortment, quantity and quality.

5.2 Assessment of the level of service provided: checklist

It will be carried out through the calculation and evaluation of the level of service provided from the internal perspective, that is, the performance of the service provided perceived by the internal customer of the inventory management. To evaluate this aspect, a procedure will be applied, in which a number of experts will be selected to whom a checklist will be applied, they will be processed through the average of the values, as a descriptive measure of trend.

1. Comprehensive analysis of problems in inventory management

An analysis of the main causes that originate the different problems detected in the diagnosis is carried out, interrelating their causes and analyzing the impact of the cost of breaking stock and its percentage with respect to total sales.

Stage 3: Design of the Inventory Management System

1. Product portfolio analysis

Selection of the products to be inventoried according to the different families.

First, the analysis of the decision criteria is carried out: Sale, Profit or Cost -according to the degree of importance raised in the strategic objectives- to make the Paretto diagram classifying the products in A, B and C. In this investigation it is chosen the criterion of Sale and Profit, grouping the A products of each paretto (Sale and Profits) in a single list, then presenting the analysis by sales.

To evaluate the importance of the products, it must be done through the classification by quadrants of the (Kralji Matrix (1984) for the classification of articles according to associated measurement criteria).

The products are classified taking into account the impact or importance of each one on the benefits to the entity, on the one hand ("Y" axis) and the complexity of their acquisition in the market on the other ("X" axis ”). The classification distinguishes the products that represent 80% of the decision criterion: Sale, Profit or Cost, which directly affects the purchase budget expense, considered as the most important for its acquisition.

The complexity of acquisition is evaluated through the number of suppliers that offer the product, the probability of availability by them, the risk in terms of its storage, the possibilities of substitution by other products and the entry barrier of new suppliers.

Once the products have been classified and according to the related factors, the positioning of each product in the matrix will be carried out and, according to the quadrant, a supply management strategy corresponds to it.

Product analysis and selection should focus on strategic items, bottlenecks, and basics (Quadrants 4, 3, and 2 respectively).

1. Forecast of product demand

8.1 Determination of the forecasting method

The demand can be classified as independent or dependent, where all dependent demand is the result of an independent one (Schroeder, 1992). Classification of methods for forecasting independent demand. The method is selected depending on the time horizon and the behavior of the components of the series: Trend, Seasonality, Cycle and Irregularity.

8.2 Forecasting demand

To facilitate calculations and obtain results more easily, different computerized statistical packages have been created, such as Statgraphics, SPSS, QSB and Microsoft Excel. In the forecast that the user only needs to interpret the results obtained.

The selection of the values ​​predicted by the different methods depends on the accuracy and veracity that is desired to be obtained, according to the stability with which it is predicted and the least error.

In this research projected independent demand products are forecast for the time horizon of one year, taking the values ​​of the sale levels of the products of the last year, proposing the forecast models of simple average, weighted average and exponential smoothing Schroeder (1992), a high forecast sensitivity will be assigned and precision will be decided by the mean absolute error (Mean Absolute Error: MAE). Microsoft Excel and SPSS software will be used.

1. Analysis of the supplier portfolio

It is important to carry out the evaluation of the suppliers according to the classification by quadrants, having the attractiveness and the negotiating power.

In the attractiveness of the suppliers, they measure criteria such as: level of service that they offer, seriousness and professionalism in the fulfillment of the contract and strength before their competitors. This investigation proposes the evaluation of providers by the level of service provided.

To define the bargaining power of the company as a client against suppliers, the following should be investigated:

• Percentage that represents the purchases of the supplier's total sales Possibility of substituting the product to be bought by others Number of suppliers in the market and position of each one Growth of the company's demand Capacity to pay Logistics situation.

Choosing in this research the last two criteria: Ease of payment credit and guarantee of the transportation service.

For the selection of suppliers, other criteria may be taken into account such as the AHP Method, called the Analytic Hierarchy Process (AHP: Analytic Hierarchy Process)

1. Determination of inventory levels

10.1 Decision on the inventory system to use

Decision-making about the inventory system to use is determined by the type of demand, whether independent or dependent.

Inventory systems can be classified as follows:

• Independent demand systems: those where demand is influenced by market conditions. Example: Deterministic inventory models and Stochastic inventory models. Dependent demand systems: those in which the demand is determined by that of other items, not receiving an influence from the market. Example: material requirement planning (MRP) and just-in-time (JIT) systems.

In this research, the economic model of stochastic inventory is chosen in which demand deficit with instantaneous replenishment is not allowed: Models of the economic optimum

10.2 Calculation of inventory system elements and determination of inventory levels

Calculation of the values ​​of quantity to order, review period, safety inventory, total cost, according to the specificity of the model. Determination of costs in inventory systems models with independent demand.

The percentages that represent the inventory levels and the cost of breaking stock are analyzed with respect to the estimate of Sales.

Calculation expressions:

1. Economic feasibility analysis

The total safety inventory (Stock) cost of the implemented inventory management system is determined, which is the sum of the estimated costs of the safety inventory referenced in Step 10, and is compared with the cost of out of stock.

According to Torres Gemeil and Co. (2007): “… This means that the decision to increase the NS is accompanied by a proportional increase in the safety inventory. Therefore, a high NS will have a higher storage cost, which is only justified when the cost of rupture is higher… "

Criterion for determining economic feasibility

The cost of safety inventory must be equal to or less than the cost of breaking stock.

Calculation expression:

If the cost generated by the estimated safety inventory levels is higher, it will have a negative impact on the financial statement reports, specifically on liquidity, but not on solvency, since the merchandise will become liquid once it is marketed, although There is a risk that due to the high level of inventory some products will become, as the year goes by, immobilized merchandise, raising immobilization costs.

In the event that the costs of the safety inventory levels are lower, a certain breakdown cost will be incurred.

Stage 4: Implementation and monitoring

Solutions should be projected based on the problems found in the diagnosis, as well as taking into account key aspects in the Negotiation and Contracting process.

1. Preparation of the program for the implementation of solutions and control

Preparation of a project of actions for the proposed solutions and implementation of the alternative, regulating the behavior of costs and controlling the system through indicators and evaluated aspects.

1. Process monitoring

Eventually continue checking the process by the techniques proposed in Phase II of diagnosis, according to the time considered by the experts.

Adjust the values ​​of the inventory management system proposed in Step 10 according to the behavior of demand over the course of the time horizon.

JOB RESULTS

The essential results of the work consist of the design of a procedure that coherently integrates the author's criteria, as well as of the various authors who propose integration procedures related to inventory management. The organization criterion of the same is conceived under a coherent structuring of stages that go from the characterization to the necessary feedback to each of the previously completed stages. It is feasible to apply in trading facilities and in companies whose products classify as independent demand.

CONCLUSIONS

1. Although the methodological approaches studied address the study of one or two of the aforementioned areas (Procurement and Distribution), they do not contemplate the integrated analysis between inventory management in retailers, which evaluate the integration between customer service and economic tools for making improvement decisions in its commercial activity, which shows the need for a conception in this order.The designed procedure is feasible and appropriate, according to expert criteria, to determine the fundamental deficiencies that affect the inventory management system and its effect for making business decisions.

RECOMMENDATIONS

1. Apply the proposed procedure to all marketers and other similar entities, checking the process and adjusting the estimated levels of the inventory management system to assess its practical validity. Follow up, through the application of the procedure, to the stages that make up the same to enrich or adjust them to the object of practical study that is selected.

BIBLIOGRAPHY

1. Álvarez and Buylla (1987). Mathematical Economic Models volume I: CUJAE, Havana City, Arbones, E. (1991). Business Logistics. Editorial ENSPES. Havana, Cuba Ballaud, RH (1991). Business Logistics. Control and Planning. Ediciones Díaz de Santos, SACaldentey, Eugenio & Pizarro, Claudio. Inventory Management. http: //www.monogramas.com Cespón Castro, R. & Auxiliadora Amador, M. (2003). Supply chain management. Central American Technological University, Unitec. Authors. (1991). Cost accounting, concepts and applications. Editorial ENSPES. Cuba, Havana. Conejero González, H., Corzo Bacallao, J. & Hernández Avila, N. (2007). Inventory Management. in universitaria, E., Río, UDPD Koontz, H. and Weihrich, H. (2008). Elements of Administration 2nd Ed.For more knowledge on the classification of Forecasting Methods, search: Hanke & Deitsch (1996) and Schroeder (1992).

   Sensitivity: “… the range of the time series that is selected (n = 1 to n = 3) has a probability that the predicted value is above the real behavior, the variance is greater…”

   Taken from: Demand and inventory forecast. Futuristic methods, by Mora Gutiérrez. Medellín First Edition. Colombia, 2007.Available at: www.softwarelabs.com

   Average Absolute Error = / Real Value of the demand - Predicted Value /

   Taken from: Fundamentals of logistics, by Torres Gemeil (2007)

   Analytical Hierarchy Method: it is framed within the so-called multicriteria optics, it allows to obtain the best provider integrally within a group, considering any number of their qualities, based on the opinions of selected experts. To go deeper into this method, see Cespón Castro and Auxiliadora Amador (2003).

   For further reference see Mathematical Economic Models Volume I Álvarez and Buylla. ISPAE Havana City, 1987.

   For a more in-depth study see: Fundamentos de Logística, by Torres Gemeil and Co. (2007)