Buyer-supplier relationships: alternative research approaches

European JournaltJfPurchasing& Supply Management,Vol. 3, No. 4, pp. 221-231, 1997 Pergamon PIi:S0969-7012(97)00022-1 © 1997 Elsevier Science Ltd All rights reserved. Printed in Great Britain 0969-7012/97 $17.00 + 0.00 Buyer-supplier relationships: alternative research approaches Rasmus Friis Olsen Institute of Production Management and Industrial Engineering, The Technical University of Denmark, Building 423 2800, Lyngby, Denmark Lisa M Ellram Arizona State University, College of Business, Department of Business Administration, Box 874706, Tempe, AZ 85287-4706, USA Buyer-supplier relationships have received considerable attention in both the purchasing and the marketing literature. This paper assesses the literature by describing a number of key articles and the research approach taken in the articles. The research approaches taken in the marketing literature, the purchasing literature and by the International Marketing and Purchasing Group (IMP Group) are compared, and advantages and disadvantages of these approaches are described. Gaps in the research are identified leading to suggestions for future research. Closer cooperation between researchers in the purchasing and the marketing field is suggested to capitalize on the relative strengths of each discipline. © 1997 Elsevier Science Ltd Keywords: buyer supplier relationship literature, buyer-supplier research perspectives Introduction This article is based on the premise that purchasing and marketing are essentially mirror images in terms of their processes, with each focusing on buyer-supplier relationships from a different perspective. An understanding of marketing/purchasing principles are essential to effectively perform the buying and selling function. The focus on buyer-supplier relationships is an example of an area of common interest between purchasing and marketing. Thus, it seems prudent to integrate research on buyer-supplier relationships between the purchasing and the marketing perspectives to fully understand the dynamics of buyersupplier relationships, to build upon each other's research, and to understand both sides of the buyer-seller dyad. This article provides an overview of the research approach taken in a number of the key articles regarding buyersupplier relationships in the purchasing and marketing literatures. It is argued that the research approaches could be combined to develop a more integrated understanding of buyer-supplier relationships. The article also identifies gaps in the research on buyer-supplier relationships by describing major streams of research on buyer-supplier relationships in the literature. The purpose of the article is to: (l) Review, analyze and classify a number of key articles (2) (3) (4) (5) on buyer-supplier relationships according to their research approach Describe streams of research and important contributions to the understanding of buyer-supplier relationships Identify differences in research approaches in the literature reviewed and describe advantages and disadvantages of the approaches Identify gaps in the research related to the research approaches used Suggest ways to close the gaps Classification of previous research To illustrate the differences in research approaches, the literature has been divided into three major groups, based upon the authors' paradigm of buyer-supplier relationships. The first group of articles to be reviewed comes from the marketing literature. The second group of articles focuses on research in the purchasing literature. Finally, the third group of articles reviewed comes from the International Marketing and Purchasing Group (IMP Group), which is a loosely joined group made up primarily of European researchers in the marketing discipline. This group was formed in the later 1970s/early 1980s. The articles written by members of the IMP group are primarily found 221 R F Olsen and L M Ellram in the marketing literature, but they have been described separately because they represent a distinct research approach and a coherent stream of research. For purposes of this article, the literatures are classified as follows: The marketingand IMP group literatureconsistsprimarily of articles from:Journal of Marketing,Journal of Marketing Research, European Journal of Marketing, Industrial Marketingand Purchasing,Industrial MarketingManagement and Journal of Business Research. The purchasing literature consists primarily articles from: InternationalJournal of Purchasingand MaterialsManagement, International Journal of Physical Distribution and Logistics Management,International Journal of Logistics Management, European Journal of Purchasing and Supply Management, and NAPM Conference Proceedings. The articles have been reviewed, analyzed, and classified based upon the research approach taken. Following the procedure suggested by Williams and Oumlil (1987) the methodology outlined by Hunt (1976) is adapted to the use in this article. To establish the type of research methodology used, the articles are classified along two dimensions. The articles were first classified as (1) empirical, (2) conceptual/ theoretical or (3) conceptual/theoretical and empirical. Empirically based articles include articles based on surveys, case studies, interviews or anecdotal information. Case studies describe and analyze buyer-supplier relationships in particular industries or product/service areas. The focus is typically narrow and in-depth, allowing the reader to thoroughly examine a limited area. Anecdotal studies give 'examples' of practices, without exploring practices in a rigorous and in-depth manner, like case studies. The articles in the conceptual/ theoretical group have their primary focus on the development of models, concepts or ideas. The articles describe Table 1 literature reviews, development of conceptual models, development of concepts or development of propositions. The articles classified as both conceptual and empirical in focus typically develop a number of hypotheses and test these hypotheses empirically. The articles were also classified as either positive/ descriptive or normative/prescriptive. The articles in the positive/descriptive category attempt to describe, explain, predict, and understand processes, activities, and phenomena that actually exist, while the articles in the normative/ prescriptive category seek to prescribe the activities in which organizations and individuals should be engaged (Hunt, 1976). The prescriptive/descriptive dimension is really a continuum, because some of the articles are primarily descriptive but give some managerial implications. In order to simplify the classification and create comparable groups of articles, the articles are only divided in prescriptive and descriptive categories based on their main focus. The following three sections describe some of the important contributions to the understanding of buyersupplier relationships found in the three groups of articles. The classification of the articles by research approach is shown under each of the three groups of articles identified and described in the next sections of the article. Due to space limitations, most of the articles are classified in the tables rather than described in the text. Marketing literature The articles from the marketing literature are classified according to their research approach in Table 1. Table 1 depicts that the majority of the articles from the marketing literature are classified as descriptive/positive and conceptual and empirical. The absence of articles in the empirical category indicates a theoretical focus in the marketing literature. The primary research approach seems Classification of the articles from the marketing literature Prescriptive/normative Empirical - survey (S) - case studies (C) - anecdotal (A) - interviews (1) Conceptual and empirical Descriptive/positive I 2 3 Conceptual/theoretical 3 Krapfel et al (1991) Spekman and Johnston (1986) The numbers indicate the research theme in the articles: 1 Characteristics and benefits of buyer-supplier relationships 2 Establishment and development of buyer-supplier relationships 3 Managing buyer-supplier relationships 222 2 Morgan and Hunt (1994) S Spekman and Mohr (1994) S Spekman and Strauss (1986) S Sriram et al (1992) S Heide and Miner (1992) S Ganesan (1994) S Heide and John (1990) S Spekman and Salmond (1990) I+S Heide and John (1992) S Noordeweir et al (1990) S Dwyer et al (1987) Spekman and Sawhney (1990) Salmond and Spekman (1986) Buyer-supplier relationships to be the development of a conceptual model, followed in some cases by an empirical testing of the model using a survey methodology. This is indicated by the 'S' after the majority of the references in Table 1. In order to provide a greater insight into the nature of issues studied in the research on buyer-supplier relationships, three recurring research themes in buyer-supplier relationships have been identified: (1) Characteristics and benefits of buyer-supplier relationships (2) Establishment and development of buyer-supplier relationships (3) Managing buyer-supplier relationships The articles classified in Table 1 will be described using these research themes in the next three sections. Characteristics and benefits of buyer-supplier relationships The research approach favored in the marketing literature appears to be build and test a path model using the survey methods. The actual benefits of buyer-supplier relationships are seldom mentioned. Morgan and Hunt (1994) use a survey to test their path model, and the results support the view that trust and commitment are mediating variables in relationship marketing. The authors also discuss the influence of power, concluding that power cannot be the central construct when explaining relationship marketing. Spekman and Mohr (1994) develop a model illustrating that partnership attributes (commitment, coordination, dependence and trust), communication behavior, and conflict resolution techniques are related to indicators of partnership success (satisfaction and sales volume in the relationship). The results of a survey used to test the model indicate that the primary characteristics of partnership success are partnership attributes of commitment, coordination and trust, communication quality and participation, and the conflict resolution technique of joint problem solving. The marketing literature on characteristics and benefits of buyer-supplier relationships is relatively sparse, so it is difficult to draw conclusions. The articles in this section are categorized as conceptual and empirical and descriptive/ positive in Table 1. Establ&hmen t and development of buyer~upplier relationships A number of articles classified in Table I describe factors affecting the establishment and development of buyersupplier relationships (Spekman and Strauss, 1986; Dwyer et al, 1987; Sriram et al, 1992; Heide and Miner, 1992; Ganesan, 1994; Heide and John, 1990; Spekman and Sawhney, 1990; Salmond and Spekman, 1986; Spekman and Salmond, 1990). The number of articles in this section indicates that factors influencing the establishment and development of buyer-supplier relationships is considered an important area of investigation in the marketing literature. The articles are primarily classified as descriptive/ positive and conceptual and empirical in Table 1. The research methodology focuses on development of hypotheses that are tested empirically using a survey methodology. Some of the articles are classified as descriptive/positive and conceptual/theoretical because the authors develop a model without testing it empirically. A common thread in this area is that transaction cost analysis is used as a theoretical basis in all the articles investigating the long-term orientation or the level of collaboration in buyer-supplier relationships in the marketing literature. The results indicate that transaction specific investments, expected continuity, the perceived uncertainty, trust, and dependence due to factors such as the product importance are among the important factors determining the long-term orientation and the level of collaboration in buyer-supplier relationships. For a greater explanation of these theories, the reader is referred to Williamson, 1985; Pfeffer and Salancik, 1978; Arndt, 1983. Managing buyer-supplier relationships A number of articles in the marketing literature describe the management of buyer-supplier relationships (Krapfel et al, 1991; Heide and John, 1992; Spekman and Johnston, 1986; Noordeweir et al, 1990). The research approaches of the articles described in this section can be divided in two groups. One group of articles is classified as prescriptive/ normative and conceptual/theoretical in Table i (Krapfel et al, 1991; Spekman and Johnston, 1986), while the other group of articles is classified as descriptive/positive and conceptual and empirical (Heide and John, 1992; Noordeweir et al, 1990). The common focus of the articles is control, dependence and power, congruent with the theoretical basis in transaction cost analysis and the resource dependence perspective. The findings support that in order to manage the relationship the company needs to gain control. Spekman and Johnston (1986) argue that the extent of control is an important factor when managing the buyer-supplier relationship. Krapfel et al (1991) use the concept of power to determine the relevant management mode. Finally, Heide and John (1992) describe how norms and transaction specific investments will influence the buyer's control over the supplier's decisions. The next section discusses the purchasing literature related to buyer-supplier relationships. Purchasing literature The articles from the purchasing literature are classified according to their research approach in Table 2. Table 2 illustrates the plethora of research approaches taken in the purchasing literature. All six categories have been used in the classification. A large group of articles are classified as descriptive/positive and empirical in Table 2, which indicate an empirical and more practitioner oriented 223 R F O/sen and L M Ellram Table 2 Classification of the articles from the purchasing literature Prescriptlve/normative Descriptive/positive Empirical - survey (S) - case studies (C) - anecdotal (A) - interviews (1) 2 1 Conceptual and empirical 1 2 Ellram (1991b) C Stuart and McCutcheon (1995) S Conceptual/theoretical 1 2 3 Landeros and Monczka (1989) Ellram (1991d) Kraljic (1983) Blenkhom and Banting (1991) Cox (1995) Cooper and Gardner (1993) Ellram (1991a) 1 Joag (1995) C 2 3 1 Ellram and Hendrick (1995) S Pilling and Zhang (1992) S Lyons et al (1990) A+I Akacum and Dale (1995) C Lascelles and Dale (1989) S+I Hendrick and Ellram (1993) S Joag et al (1992) S Stuart and Mueller (1994) C Carter and Ellram (1994) C Lamming (1993) S+I Stuart (1993) S Graham et al (1994) S Ellram (1991c) I Young et al (1993) Stuart et al (1995) The numbers indicate the research theme in the articles: 1 Characteristics and benefits of buyer-supplier relationships 2 Establishment and development of buyer-supplier relationships 3 Managing buyer-supplier relationships focus than in the marketing literature. The letters following the references in the table illustrate the use of different empirical methodologies with an emphasis on case studies and surveys. In the next three sections, the articles will be described using the same three research themes as under the marketing literature: (1) Characteristics and benefits of buyer-supplier relationships (2) Establishment and development of buyer-supplier relationships (3) Managing buyer-supplier relationships. Characteristics and benefits of buyer-supplier relationships A number of articles classified in Table 2 describe characteristics of buyer-supplier relationships (Lamming, 1986, 1993, 1995; Hines, 1995; Landeros and Monczka, 1989; Ellram and Hendrick, 1995; Ellram, 1991a; Pilling and Zhang, 1992). The large number of articles in this section indicates that one of the important areas of investigation in the purchasing literature is the characteristics and benefits of different types of buyer-supplier relationships. It is not possible to identify a common research approach based on the categorization of the articles in Table 2. A majority of the articles are descriptive/positive and the empirical methodology is primarily to use a survey methodology to investigate the actually experienced benefits of closer buyer-supplier relationships. The articles describing the characteristics of buyer-supplier relationship do not provide a coherent picture of buyer-supplier relationships, perhaps because they do not appear to represent a common stream of research, built upon each other. 224 Establishment and development of buyer-supplier relationships A number of articles describe the establishment of buyersupplier relationships (Ellram, 1991b; Stuart and McCutcheon, 1995; Young et al, 1993). The articles described in this section of the paper represent a mix of research approaches as is indicated by representation from all the categories in Table 2. In particular, the articles describing the establishment of buyer-supplier relationships represent conceptual as well as empirical articles, and descriptive as well as normative articles. The articles on success factors and barriers are primarily based on surveys or interviews in companies and describe success factors and barriers actually experienced. Important success factors include: top management support, a common view of the relationship and emphasis on establishing the communication between the buyer and the supplier. The articles describing longitudinal case studies add an ongoing monitoring of the buyer-supplier relationship to this list of important factors to consider when establishing and developing buyer-supplier relationships. An important point to make is the absence of a common terminology to describe buyer-supplier relationship which are characterized by a long-term, strategic focus. These kinds of relationships have been labelled partnerships, alliances or strategic alliances. This could indicate a lack of use of earlier research findings. This is supported by Young et al (1993) who found more than 35 different antecedents to partnership formation in 10 articles, and many of the antecedents were only found in one or two articles. Managing buyer supplier relationships The exchange of information between the buyer and the supplier is described in a number of articles (Carter and Buyer-supplier relationships The stream of research presented in the articles classified in Table 3 can be described under 4 headings: Ellram, 1994; Stuart et al, 1995). A number of articles also provide normative suggestions for the management of buyer-supplier relationships (Stuart et al, 1995; Kraljic, 1983; Blenkhorn and Banting, 1991; Cox, 1995; Cooper and Gardner, 1993). Apart from Carter and Ellram (1994), the articles in this section are conceptual and lack an empirical testing of the proposed models. The articles are primarily classified as prescriptive/normative and conceptual/theoretical in Table 2. The articles illustrate an ongoing trend towards research trying to demonstrate the benefits of closer buyersupplier relationships and research trying to establish a foundation for normative statements regarding the management of buyer-supplier relationships. As illustrated by Kraljic (1983) this is not a new approach. The next section of the article discusses the IMP-group's interaction approach and the development of their research, These headings are used instead of the three research themes identified in the marketing and purchasing literature because they can be better used to describe the development in the research by the IMP group (Ford, 1990). In Table 3, the research theme in each article is indicated by a number. The compilation of papers by Ford (1990) contains many of the articles below and summarizes the work of the IMP-group in the eighties. Each of the IMP research streams is presented below, as it is less self explanatory than the marketing or purchasing approaches. The IMP-group's interaction approach The basic concept of interaction The interaction approach was developed by a group of researchers from Europe (IMP-group) during the International Marketing and Purchasing study. The model is based upon data from a large number of case studies of buyers-supplier relationships in five European countries. The theoretical basis is Inter-Organizational Theory and transaction cost analysis. Inter-Organizational Theory is focused on the nature of the functions being performed by the system and on the structure, performance and interrelationships of the institutions which comprise the system (H~kansson, 1982). The articles by members of the IMP-group are classified according to their research approach in Table 3. Table 3 depicts that the majority of the articles written by members of the IMP group are classified as descriptive/ positive and conceptual and empirical. The overall research approach seems to be the same as in the rest of marketing literature, although the empirical methodology seems to be primarily case studies with more limited use of surveys and interviews. Table 3 • • • • The basic concept of interaction An interaction approach to purchasing The development of the interaction approach Future research - networks The basic concept of interaction is described in Cunningham (1980); Ford (1980); Ford (1984)????. Cunningham (1980) describes the IMP-group's interaction model and illustrates the use of the model by several case studies. The model provides a general understanding of buyersupplier relationships. The model contains 4 types of variables (1) Variables describing the organizations and individuals' involved in the interaction. (2) Variables describing the elements andprocess of interaction, such as products, information, financial and social exchange episodes which define the interaction process. (3) Variables describing the environment within which the interaction takes place, such as economic and social variables. (4) Variables describing the atmosphere affecting and affected by the interaction, such as power, dependence, conflict, cooperation and social distance. Classification of articles by members of the IMP group Prescriptive/normative Empirical - survey (S) - case studies (C) - anecdotal (A) - interviews (I) Conceptual and empirical 2 Descriptive/positive Turnbull and Wilson (1989) C 1 2 3 Conceptual/theoretical 3 Campbell (1985) Ford et al (1986) 2 Cunningham (1980) I+C Anderson et al (1994) Ford (1980) Hall6n e t a l (1991) C Ford (1984) S Hardwick and Ford (1986) 1 Wilson and Mummalaneni (1986) The numbers indicate the research theme in the articles: I Characteristics and benefits of buyer-supplier relationships 2 Establishment and development of buyer-supplier relationships 3 Managing buyer-supplier relationships 225 R F Olsen and L M Ellram An interaction approach to purchasing Unlike most of the work of the IMP group, which has a marketing orientation Cunningham (1980); Campbell (1985); Hardwick and Ford (1986) have a more purchasing oriented focus. Campbell (1985) expands on the work by the IMP group described in the articles listed above by developing a conceptual model outlining the strategic alternatives for purchasing and marketing. The author provides normative suggestions to conditions that will favor three different buying strategies: Competitive buying, cooperative buying and command buying and suggests typical strategies and responses to the different types of markets (buyer-supplier relationships). The development o f the interaction approach A number of articles attempt to develop new ideas on intercompany interaction, expanding on the concepts developed in the articles described above (Cunningham, 1980; Hall6n et al, 1991; Wilson and Mummalaneni, 1986; Turnbull and Wilson, 1989). Ford et al (1986) suggest that the interaction between companies is analyzed with focus on four aspects of interaction: capability, mutuality, particularity and inconsistency. The capability aspect of interaction describes what the parties can do for each other. The aspect of mutuality describes the social relations between the parties. The aspect of particularity describes the interaction in terms of direction and uniqueness. Finally, the aspect of inconsistency describes the ambiguity or lack of clarity in interaction. The authors describe in a normative way that companies should consider answering some questions regarding these aspects and the relationship among the four aspects of interaction. Future research - networks The initial model and approach by the IMP-group described in the first section was criticized, due to the absence of quantitative testing of the model (Wilson and M611er, 1988). The initial model has primarily been tested using case studies, but the results based on a survey reported in Metcalf et al (1992) seem to support the initial IMP model. The model was also criticized because it over-emphasized cooperation between companies and made little effort to understand the 'real world' of conflicts between companies (Ford, 1990). The research since the late eighties has, therefore, emphasized competitive aspects of relationships. Another weakness in the first model was the absence of technology exchanges (Ford, 1990). The research in the late eighties, such as Torelli (1986); H~tkansson (1987); H~,kansson (1989) has been focused on technology development in networks of companies. As Ford (1990) put it: 'The task is now to improve our understanding of the complexityof multiple intercompany relations in the context of higher and more rapidly changing technology' (Ford, 1990, p. 542). 226 The work of the IMP-group in recent years has expanded the idea of relationships between buyers and suppliers to relationships between all the actors in the network in which the company is embedded (Anderson et al, 1994; Easton and Axelsson, 1992; Sharma, 1993). The articles described in this section represent a clear stream of research. The members of the IMP group have focused on case studies and a relatively strong theory base to develop a model of industrial buyer-supplier relationships. They have expanded the model in response to critique and they have expanded the entire concept of relationships by placing the buyer-supplier relationship in a network context. Thus, it appears that future research of the IMP group will continue to focus on the entire network as the unit of interaction, rather than a specific dyadic relationship. The next section discusses and compares the marketing, purchasing an IMP research approaches. Comparison of research approaches This section describes the characteristics of the marketing, purchasing and IMP group research approaches and explains advantages and disadvantages of the approaches. While there is a danger in generalizing and potentially oversimplifying, the goal is to provide an overall characterization of the literature, rather than focus on exceptions. Characteristics o f research approaches Based on the classification of the articles presented here, the marketing literature focuses on the development of theory and hypotheses and in most cases, performs empirical testing of the proposed models or propositions. The empirical testing is generally based on surveys. The purchasing literature is largely empirically based and descriptive in nature. Exceptions to this pattern are Stuart (1993); Stuart and McCutcheon (1995) with a more theoretical/ conceptual approach and the literature on relationship formation and management with a more normative and theoretical approach to buyer-supplier relationships (Ellram, 1991c; Cox, 1995; Cooper and Gardner, 1993). The empirical research is most often based on surveys and case studies. The articles published by members of the IMPgroup are primarily conceptual, empirical and descriptive in nature. The empirical work is based on a large number of case studies conducted in five European countries. The marketing literature tends to focus on the micro aspects of the relationship, such as what constructs (trust, commitment, dependence, etc.) describe the relationship and how these constructs are related, developing a basic understanding of the constructs describing buyersupplier relationships. The purchasing literature is often focused on describing the outcomes of the relationship formation or the impetus for establishing certain types of relationships. Thus, the purchasing literature focuses more on the general reasons for relationship formation and reports on actual results in companies (the macro level of the relationships). The IMP approach is a mixture of Buyer-supplier relationships these two approaches. The interaction model depicts relationships on a macro level but the constructs inherent in the model, such as the variables describing the atmosphere, describe the relationship on a micro level. The marketing literature is often based on the resource dependence perspective that companies cooperate because they are dependent on resources possessed by other companies, also referred to as an open-system perspective (H6gberg, 1982). The marketing literature is frequently based on the transaction cost approach developed by Williamson. This approach implies that man is characterized by bounded rationality and opportunism. This results in a somewhat negative or pessimistic view of the possibilities of establishing closer relationships. Companies have to establish safeguards in order to protect themselves against opportunistic behavior. The purchasing literature often has a more 'positive' outlook. Companies cooperate with suppliers because the suppliers can provide resources to implement new ideas by taking part in new product development, sharing the risks and rewards of a closer relationship and contributing to the firm's overall goals. This approach is more an innovative systems view of buyersupplier relationships. In the IMP approach, Hfikansson (1982) explains the theoretical background of the interaction approach and states that it is based on a distributivesystem approach, which means that buyer-supplier relationships are viewed as interconnected institutions performing economic functions required to bring about exchange of goods and services. This is a more 'neutral' perspective on buyer-supplier relationships even though the IMP model is based on the ideas in transaction cost analysis. The marketing literature is often directed towards development of theory and has limited practical implications, while the purchasing literature often is directed towards the practical use of the research findings without a theoretical focus. The articles by the IMP group are both theoretical and practical in nature. The differences among the different streams of research are summarized in Table 4. Discussion of research approaches The marketing literature focuses on buyer-supplier relationships on a micro-level. The advantage of this approach is that it creates an understanding of the basic mechanisms of a relationship. The open-system perspective reflects a focus on the inherent drawbacks of relationship formation, for example increased dependence, the Table 4 negative influence of power and conflicts, and the risk of opportunism. These draw-backs are important to understand, if they are to be avoided. Finally, some of the articles (Krapfei et al, 1991; Heide and John, 1992; Noordeweir et al, 1990) explain the theoretical foundations of their models, which is important if the assumptions behind the research and the rationale for the model are to be understood. On the other hand, the findings from some of the articles (Morgan and Hunt, 1994; Heide and Miner, 1992; Ganesan, 1994) are very difficult for practitioners to apply. The results in these articles provide an understanding of the more basic characteristics of relationships. A number of articles (Spekman and Sawhney, 1990; Krapfel et al, 1991) also develop propositions or establish models but do not empirically test the explanatory power of these models. It is sometimes difficult to understand or see the rationale behind the way some of the constructs are defined and analyzed. Different authors use different constructs and different definitions, which creates methodological problems in comparing research results. Wilson and M611er (1988) criticize the marketing literature on this point and suggest that researchers review earlier research in order to create common definitions of constructs and facilitate a stream of research building on a common basis of theoretical and empirical results. While much of the marketing literature described in this article are published after 1988, this conclusion still appears to be true. Additionally, the marketing literature does not contain suggestions regarding how to actually chose partners for these relationships. The research in the marketing literature is generally descriptive in nature and directed towards building and testing theory. As such, it contains only few practical, normative statements. The purchasing literature focuses on the relationship at a macro level and the research tends towards an empirical approach. The advantage of the approach taken in the purchasing literature is that the findings are more applicable to practical use and can be applied to different industries. The buyer-supplier relationships are viewed positively with a focus on the opportunities available as a result of establishing closer relationships. The disadvantages of this approach is that it is difficult to establish a basic understanding of the key assumptions behind buyer-supplier relationships if the theoretical foundation is unclear and the articles are mostly empirically based. The importance of power and dependence are often overlooked. Recent articles tend to overemphasize Characteristics of research approaches - - summary Characteristic Marketing literature Purchasing literature IMP Research Approach Research methodology Research Focus Perspective Research orientation Conceptual/Empirical and descriptive Hypotheses and surveys Micro Open-System Theory development and testing Empirical and descriptive Surveys or case studies Macro Innovative-System Practical use Conceptual/Empirical and descriptive Case studies Micro/Macro Distributive-System Theory development and practical use 227 R F Olsen and L M Ellram strategic alliances/partnerships. Hendrick and Eilram, 1993 found that only a small percentage of the relationships they investigated could be described as partnerships or strategic alliances. Wilson and M611er, 1988 concluded that a framework of how to manage the entire portfolio of suppliers is missing, which still seems to be true today. The IMP interaction approach shares some of the advantages and disadvantages of both the marketing literature and the purchasing literature. The research approach is both conceptual and empirical. The strength of the IMP-model is its face validity, its strong theoretical basis, and its extensive empirical testing using case studies of over 1000 buyer-supplier relationships. The model describes both micro and macro aspects, thereby combining some of the advantages of both approaches. Some of the disadvantages of the model have been described during the presentation of the model. It is descriptive in nature and it lacks practical, normative statements and a focus on the power-dependence relations. It is important to emphasize that none of the research approaches is better than others in all aspects. Empirical research, conceptual and normative research as well as descriptive research are needed and serve specific purposes. In order to fully understand the nature of buyer-supplier relationships it is probably necessary to look at these relationships from both a micro and a macro perspective. Regarding the research perspective, it is important not to overemphasize either the positive or the negative aspects of buyer-supplier relationships. Based on this presentation, the next section describes gaps in the research. Gaps in the research - - areas requiring further investigation Based on the review, classification and analysis of the articles and the description of the streams of research on buyer-supplier relationships, a number of gaps in the literature and suggestions for future research can be put forth. The description of the gaps is organized using the same three research themes as under the marketing and purchasing literature. A section on general issues is added. The overall finding is that more normative research is needed in all research themes as well as by all of the literatures investigated here. Business is an applied field. To make a true contribution to business, researchers should provide business people with tested, usable frameworks to apply to decision making in order to improve desired outcomes. Characteristics and benefits of buyer-supplier relationships Based on the classification of the articles in Tables 1 3, it can be concluded that the articles on characteristics and benefits of buyer-supplier relationships are primarily descriptive/positive. The articles are both empirical and conceptual/theoretical. The research on characteristics and benefits of buyer-supplier relationships would benefit from a more prescriptive/normative research approach. One 228 area in particular that needs further attention is the inherent dangers of establishing closer buyer-supplier relationships. This is especially true in the purchasing literature, where there is a tendency to overemphasize close relationships, and the associated, benefits. The influence of opportunistic behavior should be investigated more closely (Morgan and Hunt, 1994). Another research area that needs closer investigation is the links between the characteristics of the relationship, such as partnership attributes (commitment, coordination and trust), conflict resolution techniques and communication behavior, and the performance or success of the relationship. The research could expand on the work by Spekman and Mohr (1994) and lead to more normative guidelines, building on previous research while providing a decision framework for practitioners. Establishment and development of buyer supplier relationships Tables 1-3 indicate that the research on establishment and development of buyer-supplier relationships is primarily descriptive/positive. Ellram (1991d); Joag (1995); Stuart and McCutcheon (1995) are exceptions. The purchasing literature on establishment and development of buyersupplier relationships is primarily empirical, while the marketing literature is both empirical and conceptual/ theoretical. It seems that this research area also could benefit from a more prescriptive/normative approach. The research on how characteristics of buyer-supplier relationships influence the success of the organizations involved could also lead to specific guidelines on establishing and developing supplier partnerships. The research on buyersupplier relationships has tended to focus on established relationships without investigating how to establish and develop buyer-supplier relationships (Joag, 1995). The establishment and development process should be investigated in more detail. A related area is the question of when to develop closer relationships. The research on buyer-supplier relationships tends to focus on partnerships or strategic alliances without questioning the reason for establishing the strategic alliance in the first place. This is particularly true in the purchasing literature, which does not have a strong theoretical grounding, such as the marketing literature's tie to transaction cost theory. Research and a strong theoretical foundation in addition to transaction cost theory is needed in this area (Ganesan, 1994). Finally, the research on buyer-supplier relationships tends to focus on a point in time. The results reported in Joag et al ( 1992); Joag (1995) illustrate the need for longitudinal studies. Longitudinal studies are especially needed to capture the dynamics of buyer-supplier relationships (Heide and Miner, 1992; Krapfel et al, 1991). Managing buyer supplier relationships As illustrated in Tables 1-3, the research on managing buyer-supplier relationships is primarily prescriptive/ Buyer-supplier relationships normative and conceptual/theoretical. It appears that empirical research is needed in this area. The starting point could be descriptive research on how managers structure the portfolio of suppliers/buyers (Krapfel et al, 1991). The research on buyer-supplier relationships has tended to focus on single relationships or a single type of relationship, such as strategic alliances. Research is needed on how to manage the entire supplier portfolio. In addition, there is a void of normative research on how to manage different types of buyer-supplier relationships. The work by Krapfel et al (1991) and the IMP group could serve as a starting point for the empirical research. The network approach developed by the IMP group suggests that the management of one buyer-supplier relationship will influence other relationships in which the company is engaged. This influence should be investigated further. General issues Based on the categorization and the description of the articles, it can be argued that the research on buyersupplier relationships in general lacks a normative focus. The authors believe that theoretically developed and tested normative research is greatly needed. Meredith, 1995 argues that development of models and theory should be based on empirical observations. There seems to be a void of empirically tested normative research. Wilson and M611er, 1988 concluded that researchers doing research on buyer-supplier relationships do not build their research on earlier results. This still appears to be true with regard to the research on buyer-supplier relationships. Researchers need to cooperate and draw on previous studies in order to avoid redundancy of research and ambiguous definitions of important constructs. This is true even within the marketing and the purchasing literatures, but is more so among the marketing, purchasing and IMP literature. Wilson and M611er (1988) suggested the development of a contingency model recognizing the range of relationships from pure market transactions to long-term relationships marked by close personal relationships. They conclude that researchers may all benefit from moving towards clarification of the key constructs and a general definition of these constructs to let them build on each other's work. It seems that the clarification and general definition of key constructs is still missing. Conclusions and suggestions In this paper, some key articles on buyer-supplier relationships have been reviewed, analyzed and classified according to their research approach. Three major groups of articles were identified: The marketing literature, the purchasing literature, and articles written by members of the IMP group. The articles in each group have been classified along two dimensions. The articles have been classified as (1) empirical, (2) conceptual/theoretical or (3) conceptual/theoretical and empirical, and the articles have been classified as either positive/descriptive or normative/ prescriptive. Important streams of research and important contributions to the understanding of buyer-supplier relationships have been identified, described and analyzed. Important contributions in the marketing and purchasing literature have been described and analyzed under three headings: (1) Characteristics and benefits of buyer-supplier relationships, (2) Establishment and development of buyer-supplier relationships, and (3) Managing buyer-supplier relationships. The differences in the research approach taken in the marketing literature, in the purchasing literature, and by the IMP group have been identified and the advantages and disadvantages of the approaches have been described. Finally, gaps in the research have been described. Gaps in the research have been found under all three headings noted above. It appears that a common base of theory and empirical research from which future theoretical and empirical research can be developed needs to be established. Using Rudner's (1966) definition of theory, this means that researchers in the field of buyer-supplier relationships need to establish a systematic related set of statements. This should include definitions and some law like generalizations to be developed as empirically testable hypotheses. The theoretical basis should increase scientific understanding through a systematized structure capable of both explaining and predicting phenomena (Rudner, 1966). The theoretical basis should, therefore, consist of common definitions of important constructs, such as trust, commitment, power and dependence, and theoretical models describing different aspects of buyer-supplier relationships, such as the IMP interaction model, and the relationship between the constructs. It is important that the theory basis is recognized by a large number of the researchers in the field in order to create a coherent stream of research on buyer-supplier relationships. The theory developed should emphasize all three research streams reviewed here: characteristics and benefits of buyersupplier relationships, establishment and development of buyer-supplier relationships and managing buyersupplier relationships. The research should be normative as well as descriptive. What type of relationship is best in a given situation? How should relationships best be managed on an ongoing basis? The most coherent stream of research described above is the work by the IMP group. The establishment and development of the IMP group could serve as a benchmark for future research efforts in buyer-supplier relationships. A more formalized group of researchers could help establishing the common basis for research on buyersupplier relationships. One lesson learned from the establishment of the IMP group is that it is very time consuming to have formalized meetings (H~kansson, 1982). Forming a loose network of researchers using the Internet could be a step in the right direction because researchers from all over the world would be able to exchange ideas and research results. The idea of establishing a database is currently underway by both International Purchasing and Supply Education and Research Association (IPSERA) and 229 R F Olsen and L M Ellram National Association of Purchasing Management (NAPM), both professional purchasing organizations. It would be easily technologically feasible to network with researchers all over the world who share common interests. It should be emphasized that it is important to also create the connections to researchers in the marketing field. To summarize, at least four important tasks can be identified in relation to strengthening future research in buyer-supplier relationships. (1) Extension of the cooperation between researchers within purchasing and marketing. (2) Establishment of a common definition of constructs. (3) Creation of formal and/or informal networks. (4) Research in the areas where gaps have been identified, particularly grounded, normative research. This article is only a starting point on the path to the establishment of a common theoretical and empirical basis in research on buyer-supplier relationships. Much work needs to be done. Given the differences in perspective and methodology between purchasing and marketing research this will be a formidable challenge. However, the potential benefits and synergies of addressing the important aspect of creating a common theoretical and empirical basis in the researching on buyer-supplier relationships are great enough to surmount this challenge. References Akacum, A. and Dale, B. G. (1995) Supplier partnering: case study experiences.. 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He holds a Masters degree in production management and industrial engineering from The Technical University of Denmark. The work was initiated while he was a visiting scholar at Department of Business Administration, Arizona State University. Lisa Ellram, C.EM., CPA, is Associate Professor of Supply Chain Management at Arizona State University. She received her Ph.D degree from the Ohio State University. Dr. Ellram's major research interests are buyer-supplier relationships, including supply chain management, purchasing strategy, and total cost of ownership/cost management. 231