O funcionamento da cadeia de suprimentos é um tema atual que tem motivado muitas pesquisas para o entendimento da sua dinâmica como fonte de obtenção de vantagem competitiva. O bullwhip effect - efeito de oscilação de demanda dentro da cadeia de suprimentos - é um dos causadores de ineficiências operacionais e de consequentes gastos desnecessários. Esse fenômeno ainda não foi estudado em sua totalidade; a maioria das pesquisas até então utilizaram-se de análises quantitativas, não levando em conta fatores qualitativos presentes em situações de oscilação de demanda, tais como: a experiência do programador de demanda, as capabilidades desenvolvidas pela empresa e os métodos que ela utiliza para integrar o conhecimento sobre o fenômeno. Esta pesquisa contribui nesse sentido. Coloca em evidência, por meio da análise qualitativa do bullwhip effect e dos fundamentos do processo de capacidade absortiva. Busca-se integrar esses dois conceitos, até então não abordados conjuntamente. A reunião desse referencial e dos resultados obtidos por intermédio das observações deverá fornecer subsídios para a melhor compreensão do fenômeno. A estratégia de pesquisa selecionada se deu por meio de estudos de caso com três empresas brasileiras, de diferentes setores. Entrevistaram-se sete executivos das empresas, responsáveis pela programação da produção e a análise de demanda. Foram encontrados muitos pontos convergentes entre a literatura e a prática empresarial, principalmente sobre os fundamentos da capacidade absortiva em uma situação de bullwhip effect, como também entre as diferentes dimensões da capacidade absortiva per se. A principal contribuição da pesquisa está em integrar orientações teóricas e ações práticas desenvolvidas pelas empresas sob o bullwhip effect, relacionadas com a capacidade absortiva, dando destaque aos fatores humanos, o que propicia um referencial mais abrangente para examinar esses processos. Em nível gerencial, oferece-se subsídios aos gestores no aprimoramento de técnicas de absorção do conhecimento em situações de oscilação de demanda, tornando suas previsões e a produção mais eficientes. / The operation of the supply chain is a current topic and it has motivated many researches in order to understand its dynamic as source of obtaining competitive advantage. The bullwhip effect - the effect of oscillating demand inside the supply chain - is one of the originators of operational inefficiencies and consequent unnecessary expenditure. This phenomenon has not been studied in its totality yet; most researches have used quantitative analysis so far, not taking into account qualitative factors which are present in oscillating demand situations, such as: the experience of the demand manager, the capabilities developed by the company and the methods which it uses to integrate the knowledge about the phenomenon. This research contributes in this sense. It highlights through the bullwhip effect qualitative analysis and the process fundamentals of absorptive capacity. It pursuits to integrate these two concepts which have not thus far been approached together. The reunion of this reference and the obtained results through remarks should provide subsidies for better comprehension of the phenomenon. The research strategy selected was through case studies with three Brazilian companies of different sectors. Seven executives of the companies were interviewed; they are responsible for the production programming and for the demand analysis. Many convergent points were found between literature and the business practice, mainly concerning the fundamentals of absorptive capacity in a bullwhip effect situation, as well as among the different dimensions of absorptive capacity per se. The main contribution of the research is to integrate theoretical orientations and practical actions developed by the companies under the bullwhip effect, which are related to the absorptive capacity, highlighting to the human factors, which provides a reference more comprehensive to examine these processes. In a managerial level, subsidies are offered to the managers in the improvement of the absorption techniques of the knowledge in oscillating demand situations, making their forecasts and the production more efficient.

In this study, I have developed the theoretical concept Service Bullwhip Effect (SBWE) by examining it within the professional services context through a single case study at a Swedish consultancy firm. The research questions that have been guiding the study are the following: F1. How does the service bullwhip effect differ in professional service firms compared with other service firms? F2. How can the service bullwhip effect be mitigated within professional service firms? The purpose of the study is thus to contribute to the research area of Service Supply Chain Management, and its theoretical concept SBWE. I do this by studying the SBWE within the context of professional service firms (PSF), and analyze how it differentiate itself from other service firms, and how it can be mitigated within this context. The methodology used have been a combination of data sources that were collected in the form of primary qualitative data, and secondary quantitative data from the service supply chain of a consultancy firm. My findings indicate that a SBWE exists to some extent within the professional services context. Its presence, however, was limited due to the inherent characteristics of PSFs. From this I put forward the following three propositions: H1. The service bullwhip effect exists to some extent within professional service firms, and primarily in the form of a negative effect due to a work underdelegation. H2. Shortage gaming does not exist within the professional services context due to the close relation these firms have with its customers. H3. Batch ordering exists within professional service firms in the form of project clusters. Furthermore, managerial recommendations are also provided on how to mitigate the SBWE within the PSFs. My findings points towards a reduced emphasis on the individual utilization rate for the more senior consultants within the firm. Instead, I see that a larger emphasis should be put on the economic performance of projects when evaluating consultants that are project leaders. Research implications & limitations - As a single case, the research achieves a significant depth within the studied consultancy context, but have a limited generalizability. Therefore, the developed propositions will need to be tested within other types of PSFs, and thus with different sets of characteristics. / I denna studie har jag byggt vidare på teorier kopplade till Service Bullwhip Effect (SBWE) genom att undersöka konceptet inom den kunskapsintensiva tjänstesektorn. Detta har jag gjort genom en fallstudie på analys- och teknikkonsultföretaget WSP i form av en kvalitativ och kvantitativ datainsamling. Den insamlade empirin jämfördes med resultat från tidigare studier för att analysera huruvida SBWE existerar inom kunskapsintensiva tjänsteverksamheter, och hur denna effekt i så fall skiljer sig från andra tjänsteverksamheter. Utifrån analysen har jag fört en diskussion med koppling till de forskningsfrågor som styrt studien: F1. Hur skiljer sig Service Bullwhip Effect inom kunskapsintensiv tjänsteverksamhet jämfört med andra tjänsteverksamheter? F2. Hur kan Service Bullwhip Effect hanteras inom en kunskapsintensiv tjänsteverksamhet? Studiens slutsatser utifrån den första forskningsfrågan (F1) pekar bland annat på att en SBWE existerar till viss del inom kunskapsintensiva tjänsteföretag. Dock inte i samma utsträckning som inom icke kunskapsintensiva tjänsteverksamheter. Dessa slutsatser summeras i form av tre nya hypoteser: H1. The Service Bullwhip Effect existerar till viss del inom kunskapsintensiv tjänsteverksamhet, och främst i form av en negativ effekt på grund av en underdelegation av arbetsuppgifter. H2. Shortage Gaming existerar inte inom kunskapsintensiv tjänsteverksamhet på grund av den nära relationen med kunderna. H3. Batch ordering existerar inom kunskapsintensiv tjänsteverksamhet i form av uppdragskluster. De dragna slutsatserna konfirmerar därmed teorierna inom området samtidigt som branschspecifika adapteringar av teorin föreslås utifrån de särskilda förhållandena som råder inom den kunskapsintensiva tjänstesektorn. Dessa slutsatser har dock en låg generaliserbarhet och validitet då jag i denna studie undersökt ett specifikt fall, och därmed presenterar jag mina slutsatser i form av hypoteser som kräver testning genom ytterligare studier. Slutligen ger jag ledningsmässiga rekommendationer utifrån den andra forskningsfrågan (F2). Dessa rekommendationer har sitt fokus på hur SBWE kan motverkas utifrån det specifika fallet inom konsultföretaget, och hur en rådande underdelegation kan bearbetas av verksamhetens ledning. För att motverka SBWE, och en underdelegation av arbetsuppgifter, så rekommenderar jag bland annat att seniorkonsulterna utvärderas med en låg prioritet utifrån deras beläggningsgradskrav, och med hög prioritet utifrån deras ansvar över uppdragsekonomin.

The bullwhip effect is defined as an upstream amplification of demand variability and has received interest within multinational companies for decades. As early as in the 1950’s, Forrester (1958) discussed what is today known as the bullwhip effect, which has a negative impact on the customer service, costs, and inventory investment in a supply chain (Lee et al., 1997). Even though the bullwhip effect has been noticed in various industries, the consequences, in form of decreased availability and increased costs the further up the supply chain the bullwhip goes, still remain. The employees at Volvo Group Service Market Logistics suspect that their supply chain has been affected by the bullwhip effect and want to know if it is correct and subsequently know why it has occurred. Therefore, this master’s thesis highlights the root causes of the bullwhip effect and presents strategies to mitigate it. To understand how the bullwhip effect affected the Volvo Group Service Market Logistics’ supply chain, the purpose was formulated as follow: The purpose of this study is to identify events in the Volvo Group Service Market Logistics’ supply chain where the bullwhip effect has occurred, its root causes, and how to reduce or eliminate the bullwhip effects.  The studied flow was from the Central Distribution Center (CDC) in Ghent, to the Regional Distribution Center (RDC) in Brazil, to the Dealers associated to the RDC in Brazil, and the customers. Data was collected from each node and events were studied to find bullwhip events. After sorting out the part numbers that passed the criteria for bullwhip events, the amount of data had to be reduced even more. A couple of different conditions were applied which resulted in four suitable bullwhip events. Thereafter, the authors conducted interviews with Logistics Managers at each node of the supply chain to find the root causes of the bullwhip effect in each studied event.  Among the several found root causes, lack of information transparency was the most frequent occurring root cause, found in three out of four studied bullwhip events. Insufficient communication and lack of information sharing cause bullwhip effects, and the authors found that improved communication both between and within the nodes will contribute to better planning, and consequently avoided bullwhip effects. Other root causes found were issues with the ordering system, lack of learning and experience, neglected lead times, fear of empty stock, price fluctuations, and phase-out of the spare part.  To reduce or eliminate the bullwhip effect, the focus was on mitigating the root causes since the root causes create opportunities for the bullwhip effect to occur. Four suggestions were given with suitable mitigation strategies found in the literature, where the four suggestions were sales campaigns, prepare for boosts, keep track of manually placed orders, and ordering system and Logistics Manager behavioural issues. The suggestions could then be connected to the different found root causes. The stated suggestions and mitigation strategies focused on mitigating the root causes in a long-term perspective and consequently the bullwhip effect itself.

This thesis explores Centralised Demand Information Sharing (CDIS) in supply chains. CDIS is an information sharing approach where supply chain members forecast based on the downstream member’s demand. The Bullwhip Effect is a demand variance amplification phenomenon: as the demand moves upstream in supply chains, its variability increases. Many papers in the literature show that, if supply chain members forecast using the less variable downstream member’s demand, this amplification can be reduced leading to a reduction in inventory cost. These papers, using strict model assumptions, discuss three demand information sharing approaches: No Information Sharing (NIS), Downstream Demand Inference (DDI) and Demand Information Sharing (DIS). The mathematical analysis in this stream of research is restricted to the Minimum Mean Squared Error (MMSE) forecasting method. A major motivation for this PhD research is to improve the above approaches, and assess those using less restrictive supply chain assumptions. In this research, apart from using the MMSE forecasting method, we also utilise two non-optimal forecasting methods, Simple Moving Averages (SMA) and Single Exponential Smoothing (SES). The reason for their inclusion is the empirical evidence of their high usage, familiarity and satisfaction in practice. We first fill some gaps in the literature by extending results on upstream demand translation for ARMA (p, q) processes to SMA and SES. Then, by using less restrictive assumptions, we show that the DDI approach is not feasible, while the NIS and DIS approaches can be improved. The two new improved approaches are No Information Sharing – Estimation (NIS-Est) and Centralised Demand Information Sharing (CDIS). It is argued in this thesis that if the supply chain strategy is not to share demand information, NIS-Est results in less inventory cost than NIS for an Order Up To policy. On the other hand, if the strategy is to share demand information, the CDIS approach may be used, resulting in lower inventory cost than DIS. These new approaches are then compared to the traditional approaches on theoretically generated data. NIS-Est improves on NIS, while CDIS improves on the DIS approach in terms of the bullwhip ratio, forecast error (as measured by Mean Squared Error), inventory holding and inventory cost. The results of simulation show that the performance of CDIS is the best among all four approaches in terms of these performance metrics. Finally, the empirical validity of the new approaches is assessed on weekly sales data of a European superstore. Empirical findings and theoretical results are consistent regarding the performance of CDIS. Thus, this research concludes that the inventory cost of an upstream member is reduced when their forecasts are based on a Centralised Demand Information Sharing (CDIS) approach.

Purpose – The purpose of the research is to explore how to reduce waste in value flows and to minimize the bullwhip effect within operations. To fulfill and answer the purpose of the research three questions of issue has been established: 1. What issues in value flows can be identified, regarding inbound and outbound flows? 2. How can issues in value flows be minimized, with regards to inbound and outbound flows? 3. How can a model be created to understand the relationship between value flow improvements and the bullwhip effect? Method – To retrieve understanding of the topic that thesis involves, support of literature studies, observations and data collection was used. The literature study created a foundation of theoretical framework. The data collected from the case company formed a base that partly facilitates the purpose of this thesis. The theoretical framework and data collection were thoroughly analyzed and discussed in order to propose solutions for improvements. Findings – The research establishes different issues that can be identified in outbound and inbound flows such as; waste in transportation, waste in inventory, waste in movement and waste in overproduction. Further, in order to minimize the identified issues in inbound and outbound flows it is imperative to find out the root cause for the issues. When the root cause was established, statistical approach was utilized to further explain the issue. The findings from the statistical approach elucidated a large variance between supply and demand, resulting in a bullwhip effect. In order to minimize the bullwhip effect, improvements should focus on insufficiencies such as; lack of communication, order batching and disorganization. In addition, standardization through 5s approach mitigates the waste in transportation and movement. To understand the relationship between value flow improvements and the bullwhip effect, a causal loop diagram was created to understand the phenomenon from a system perspective. Implications – The research contributes with solutions on how to identify the bullwhip effect as well as highlighting the issues in value flows. Furthermore, this research solidifies the importance of using lean process to improve overall productivity in value flows. Limitations – The research was limited to one case company and one area in the case company. The answers that are presented in this research could increase the reliability and credibility if the authors had been able to investigate several areas at the case company or several companies. Furthermore, the date that has been retrieved is based solely on one supplier at the case company. Keywords – ‘Lean Process’, ‘Bullwhip Effect’, ‘Supply Chain Management’, ‘Continuous Improvement’, ‘System Perspective’ and ‘Statistical Analysis’.

In this work bullwhip effect in the supply chains was studied and reduction of the effect was analyzed. Simulation was done with Rockwell Arena software. Eight different models were created using two different bullwhip reduction schemes (batching removal and information sharing) with two different ordering distributions (normal and exponential distribution). Analyzed supply chain consisted of two groups of customers, two distributors, one manufacturer and two suppliers, producing different components for manufacturer. Information processing, lead and manufacturing times where stochastic values. Analysis is based on the mean value and standard deviation of orders and inventory level. Research showed, that most effective bullwhip reduction scheme is information sharing which let to reduce supplier’s inventory level up to 90%. Also effect reduction schemes are more effective when order variability is greater. This work is primary supply chain model. Therefore author offers to continue this work and do next analysis: to analyze other order distributions’ and other stochastic model variables influence to bullwhip reduction schemes, to analyze other supply chain structures, to do mathematical evaluation.

Baigiamajame magistro darbe nagrinėjama viena iš pagrindinių tiekimo grandinių valdymo problemų ─ neapibrėžtumo efektas, didinantis įmonių veiklos sąnaudas, sandėlio lygį ir mažinantis konkurencingumą. Pagrindinis baigiamojo darbo tikslas yra pateikti galimus neapibrėžtumo efekto mažinimo būdus tiekimo grandinėse. Darbe yra analizuojama neapibrėžtumo efekto samprata, įtaka tiekimo grandinėms, identifikavimo būdai, atsiradimo priežastys ir efektą mažinančių priemonių panaudojimo efektyvumas. Išnagrinėjus teorinius ir praktinius neapibrėžtumo efekto aspektus, pateikiamos baigiamojo darbo išvados ir siūlymai. Darbą sudaro 5 dalys: įvadas, analitinė-metodinė, eksperimentinė-tiriamoji dalis, išvados ir siūlymai, literatūros sąrašas. Darbo apimtis – 62 p., 23 iliustr., 4 lent., 34 bibliografiniai šaltiniai. Atskirai pridedami darbo priedai. / The main topic of this thesis is bullwhip effect, under which influence negative factors such as increased warehouse level, demand variations, big internal expenditures and decreased competition can seriously affect efficiency of whole supply chain. The main goal of this thesis is suggest possible ways of bullwhip effect reduction in supply chain. In this is thesis author is analyzing: conceptions of bullwhip effect influence on supply chain, ways of effect identification; search for methods to decrease bullwhip effect. Main tolls of bullwhip effect reduction are: proper information sharing; reducing of shipment transportation time; using of efficient demand forecasting method; development of VMI system, and installation of up-to-date IT systems. Structure: introduction, analytical part, experiment, conclusions and suggestions, references. Thesis consist of: 62 p., 23 pictures, 4 tables, 34 bibliographical entries. Appendixes included.

O aumento da variabilidade da demanda ao longo de uma cadeia de abastecimento é conhecido como Efeito Chicote (EC). A modelagem deste fenômeno é fundamental para a quantificação de sua intensidade, ajudando a reduzir seus impactos negativos sobre o nível de serviço e sobre os estoques em uma cadeia de abastecimento. Esta tese apresenta uma proposta de modelagem do EC que tem por objetivo aumentar a precisão na quantificação deste fenômeno em ambientes com demanda e lead time estocásticos. O novo modelo considera dois elementos que não estão presentes nos principais modelos disponíveis na literatura: a variabilidade no lead time de entrega de pedidos e a incorporação de um ajuste para contemplar uma política adequada de tratamento dos excessos de estoque. Além disso, define de modo mais preciso o papel do coeficiente de variação da demanda na quantificação do EC. A utilização do modelo proposto aumenta a eficiência da gestão de cadeias de abastecimento ao contribuir para atenuar a propagação do EC, elevar o nível de serviço e reduzir os níveis local e global dos estoques. Neste documento, os principais modelos de quantificação do EC são apresentados e analisados, com destaque para os trabalhos de Lee et al. (1997b), Chen et al. (2000), Fransoo e Wouters (2000) e Warburton (2004); nessa análise foram identificadas várias deficiências, capazes de produzir fortes distorções no processo de quantificação do EC. O modelo proposto supre integralmente estas deficiências e apresenta elementos que indicam que a intensidade e o comportamento estocástico e serial do EC só podem ser adequadamente modelados se a variabilidade do lead time for considerada e se os excessos de estoque forem utilizados no cálculo do tamanho dos pedidos. O novo modelo, além de contribuir para o entendimento da dinâmica do EC e para a ampliação do respectivo campo de discussão, representa adequadamente a complexidade das relações entre as variáveis associadas ao EC, o que lhe confere alta capacidade preditiva. Complementarmente, demonstra-se que o modelo de Chen et al. (2000) constitui um caso particular do modelo proposto. / The increase in demand variability as information flows from customers to manufacturers in a supply chain is known as the Bullwhip Effect (BE). Modeling this phenomenon is fundamental in measuring its intensity, aiming at reducing its negative impacts on both service and inventory levels in the supply chain. In this dissertation we propose a new, more precise mathematical model for quantifying the BE in systems with stochastic demand and lead time. The new model takes into account the lead time variability and is adjusted to a more realistic treatment of negative order quantities that may arise in some inventory cycles, two elements not present in the main available models in the literature. In addition, the model enables a more precise assessment of the role that the demand coefficient of variation plays in the quantification of the BE. The use of the proposed model enables an improved management of the supply chain by attenuating the propagation of the BE, increasing the service level and reducing inventory levels both locally and globally. In this dissertation, the main models for quantifying the BE are presented and analyzed, with emphasis in the works of Lee et al. (1997b), Chen et al. (2000), Fransoo and Wouters (2000) and Warburton (2004); in that analysis were identified several deficiencies, able to generate severe distortions in the quantification of the BE. The proposed model fully overcomes these deficiencies and presents elements that indicate that the intensity and stochastical and serial behavior of the BE can only be appropriately modeled if the lead time variability is considered and if inventory excesses are used in the order size calculation. The new model, in addition to contribute to the understanding of the BE dynamics enriching its analysis, represents appropriately the complexity of relationships among variables associated with the BE, contributing to its high predictive capacity. Finally, it is demonstrated that the model in Chen et al. (2000) represents a special case of the proposed model.

O aumento da variabilidade da demanda ao longo de uma cadeia de abastecimento é conhecido como Efeito Chicote (EC). A modelagem deste fenômeno é fundamental para a quantificação de sua intensidade, ajudando a reduzir seus impactos negativos sobre o nível de serviço e sobre os estoques em uma cadeia de abastecimento. Esta tese apresenta uma proposta de modelagem do EC que tem por objetivo aumentar a precisão na quantificação deste fenômeno em ambientes com demanda e lead time estocásticos. O novo modelo considera dois elementos que não estão presentes nos principais modelos disponíveis na literatura: a variabilidade no lead time de entrega de pedidos e a incorporação de um ajuste para contemplar uma política adequada de tratamento dos excessos de estoque. Além disso, define de modo mais preciso o papel do coeficiente de variação da demanda na quantificação do EC. A utilização do modelo proposto aumenta a eficiência da gestão de cadeias de abastecimento ao contribuir para atenuar a propagação do EC, elevar o nível de serviço e reduzir os níveis local e global dos estoques. Neste documento, os principais modelos de quantificação do EC são apresentados e analisados, com destaque para os trabalhos de Lee et al. (1997b), Chen et al. (2000), Fransoo e Wouters (2000) e Warburton (2004); nessa análise foram identificadas várias deficiências, capazes de produzir fortes distorções no processo de quantificação do EC. O modelo proposto supre integralmente estas deficiências e apresenta elementos que indicam que a intensidade e o comportamento estocástico e serial do EC só podem ser adequadamente modelados se a variabilidade do lead time for considerada e se os excessos de estoque forem utilizados no cálculo do tamanho dos pedidos. O novo modelo, além de contribuir para o entendimento da dinâmica do EC e para a ampliação do respectivo campo de discussão, representa adequadamente a complexidade das relações entre as variáveis associadas ao EC, o que lhe confere alta capacidade preditiva. Complementarmente, demonstra-se que o modelo de Chen et al. (2000) constitui um caso particular do modelo proposto. / The increase in demand variability as information flows from customers to manufacturers in a supply chain is known as the Bullwhip Effect (BE). Modeling this phenomenon is fundamental in measuring its intensity, aiming at reducing its negative impacts on both service and inventory levels in the supply chain. In this dissertation we propose a new, more precise mathematical model for quantifying the BE in systems with stochastic demand and lead time. The new model takes into account the lead time variability and is adjusted to a more realistic treatment of negative order quantities that may arise in some inventory cycles, two elements not present in the main available models in the literature. In addition, the model enables a more precise assessment of the role that the demand coefficient of variation plays in the quantification of the BE. The use of the proposed model enables an improved management of the supply chain by attenuating the propagation of the BE, increasing the service level and reducing inventory levels both locally and globally. In this dissertation, the main models for quantifying the BE are presented and analyzed, with emphasis in the works of Lee et al. (1997b), Chen et al. (2000), Fransoo and Wouters (2000) and Warburton (2004); in that analysis were identified several deficiencies, able to generate severe distortions in the quantification of the BE. The proposed model fully overcomes these deficiencies and presents elements that indicate that the intensity and stochastical and serial behavior of the BE can only be appropriately modeled if the lead time variability is considered and if inventory excesses are used in the order size calculation. The new model, in addition to contribute to the understanding of the BE dynamics enriching its analysis, represents appropriately the complexity of relationships among variables associated with the BE, contributing to its high predictive capacity. Finally, it is demonstrated that the model in Chen et al. (2000) represents a special case of the proposed model.

O aumento da variabilidade da demanda ao longo de uma cadeia de abastecimento é conhecido como Efeito Chicote (EC). A modelagem deste fenômeno é fundamental para a quantificação de sua intensidade, ajudando a reduzir seus impactos negativos sobre o nível de serviço e sobre os estoques em uma cadeia de abastecimento. Esta tese apresenta uma proposta de modelagem do EC que tem por objetivo aumentar a precisão na quantificação deste fenômeno em ambientes com demanda e lead time estocásticos. O novo modelo considera dois elementos que não estão presentes nos principais modelos disponíveis na literatura: a variabilidade no lead time de entrega de pedidos e a incorporação de um ajuste para contemplar uma política adequada de tratamento dos excessos de estoque. Além disso, define de modo mais preciso o papel do coeficiente de variação da demanda na quantificação do EC. A utilização do modelo proposto aumenta a eficiência da gestão de cadeias de abastecimento ao contribuir para atenuar a propagação do EC, elevar o nível de serviço e reduzir os níveis local e global dos estoques. Neste documento, os principais modelos de quantificação do EC são apresentados e analisados, com destaque para os trabalhos de Lee et al. (1997b), Chen et al. (2000), Fransoo e Wouters (2000) e Warburton (2004); nessa análise foram identificadas várias deficiências, capazes de produzir fortes distorções no processo de quantificação do EC. O modelo proposto supre integralmente estas deficiências e apresenta elementos que indicam que a intensidade e o comportamento estocástico e serial do EC só podem ser adequadamente modelados se a variabilidade do lead time for considerada e se os excessos de estoque forem utilizados no cálculo do tamanho dos pedidos. O novo modelo, além de contribuir para o entendimento da dinâmica do EC e para a ampliação do respectivo campo de discussão, representa adequadamente a complexidade das relações entre as variáveis associadas ao EC, o que lhe confere alta capacidade preditiva. Complementarmente, demonstra-se que o modelo de Chen et al. (2000) constitui um caso particular do modelo proposto. / The increase in demand variability as information flows from customers to manufacturers in a supply chain is known as the Bullwhip Effect (BE). Modeling this phenomenon is fundamental in measuring its intensity, aiming at reducing its negative impacts on both service and inventory levels in the supply chain. In this dissertation we propose a new, more precise mathematical model for quantifying the BE in systems with stochastic demand and lead time. The new model takes into account the lead time variability and is adjusted to a more realistic treatment of negative order quantities that may arise in some inventory cycles, two elements not present in the main available models in the literature. In addition, the model enables a more precise assessment of the role that the demand coefficient of variation plays in the quantification of the BE. The use of the proposed model enables an improved management of the supply chain by attenuating the propagation of the BE, increasing the service level and reducing inventory levels both locally and globally. In this dissertation, the main models for quantifying the BE are presented and analyzed, with emphasis in the works of Lee et al. (1997b), Chen et al. (2000), Fransoo and Wouters (2000) and Warburton (2004); in that analysis were identified several deficiencies, able to generate severe distortions in the quantification of the BE. The proposed model fully overcomes these deficiencies and presents elements that indicate that the intensity and stochastical and serial behavior of the BE can only be appropriately modeled if the lead time variability is considered and if inventory excesses are used in the order size calculation. The new model, in addition to contribute to the understanding of the BE dynamics enriching its analysis, represents appropriately the complexity of relationships among variables associated with the BE, contributing to its high predictive capacity. Finally, it is demonstrated that the model in Chen et al. (2000) represents a special case of the proposed model.