Organizational Servant Leadership: A Systematic Literature Review for Implications in Business

The leadership of servants is a new research area linked to ethics, virtues, and morality. As critics debate whether this new leadership theory is significantly distinct, viable, and valuable for organizational success, scholars are currently looking for publication outlets. The objective of this research was to identify empirical studies that explored the theory of servant leadership by involving a sample population to evaluate and synthesize the mechanisms, results, and impacts of servant leadership. Therefore, we were trying to provide an evidence-informed answer to how the ship's servant leader works and how can we apply it? To synthesize research in a systematic, transparent and reproducible way, we conducted a systhematic literature review (SLR), a methodology adopted from the medical sciences. A disciplined screening process resulted in 39 appropriate studies of the final sample population. The synthesis of these empirical studies revealed: (a) there is no consensus on the definition of servant leadership; (b) the theory of servant leadership is being studied in a variety of contexts, cultures, and themes; (c) researchers use multiple measures to explore servant leadership, and (d) servant leadership is a viable theory of leadership that helps organizations and enhances us. This research helps to develop the leadership of servants. Theory and exercise. Furthermore, this research contributes to the methodology for conducting SLRs in the field of management, highlighting an efficient method for thematically mapping and holistic viewing of new research topics. By offering suggestions for future research, we conclude.


INTRODUCTION
Leadership is one of the behavioral sciences' most comprehensively researched processes of social influence. This is because all economic, political, and organic systems' success depends on these systems' leaders' effective and efficient guidance (Barrow 1977). A critical factor in understanding an organization's success, then, is studying its leaders. Leadership is a skill used in an organization to influence followers to work enthusiastically towards goals specifically defined for the common good (Barrow 1977;Cyert 2006;Plsek and Wilson 2001). Great leaders create an organizational vision, articulate the vision to the supporters, create a shared vision, develop a path to achieve the vision, and guide their organizations in new directions (Banutu-Gomez and Banutu-Gomez 2007;Kotter 2001). According to Schneider (1987), the people in it, including the followers (i.e., staff and volunteers) and the leaders, are the most important part of building an organization with a legacy of success. Leadership theories attempt to explain and organize the complexity and consequences of leadership's nature (Bass and Bass 2008). The implicit connection between ethics and leadership has been called to attention by some leadership scholars over the years. Servant leadership is a burgeoning new research and leadership theory that has been linked to ethics, virtues and morality (Graham 1991;Lanctot and Irving 2010;Parolini et al. 2009;Russell 2001;Whetstone 2002).
The emphasis of Servant Leadership Theory on service to others and recognize that the role of organizations is to create individuals who can build a better tomorrow resonates with scholars and practitioners who respond to the growing perceptions that corporate leaders have become selfish and seek a viable theory of leadership to help solve the challenges of the twenty-first century. Although Robert K. Greenleaf coined servant leadership more than three decades ago in 1970, it remains understudied but still prominently practiced in boardrooms and organizations (Bass and Bass 2008;Spears 2005). The popular press (e.g., Fortune magazine and Dateline) (Spears Center, 2011) has received significant attention and leading organizational leadership. Some studies have discussed the beneficial effects of servant leadership on organizational profits and employee satisfaction (DePree, 1989;Covey, 1990;Senge, 2005). However, the conceptualization of servant leadership as a way of life rather than a management technique by Greenleaf (1977) may have slowed the acceptance of this leadership theory in academia, as scholars ask the question: if it is a way of life, how can it be empirically tested? Even the admitted servant leadership of Greenleaf is unorthodox and would be difficult to operate and apply, as " it is not meant to be a scholarly treatise or a how-to-do-it manual " (Greenleaf 1977, p. 49). The majority of research to date on servant leadership involves developing theoretical frameworks and establishing measurement tools to enable future scholars to use these tools in practice and as a tenable theory to explore servant leadership. A limited amount of research has empirically examined this construct.
We sought to identify these empirical studies that investigated servant leadership by engaging a sample population in order to evaluate and synthesize its mechanisms, results, and impacts as an aid in advancing servant leadership theory. There is currently no comprehensive summary of empirical studies exploring the theory of servant leadership in organizational environments (e.g., a systematic literature review (SLR)), which is a gap in existing literature. We provide evidence that servant leadership is a tenable theory by exploring empirical studies investigating servant leadership theory in organizational contexts.
As a promising new field of research, servant leadership faces the challenges once addressed by early service marketing and sports management scholars whose new ideas and concepts were slowly adopted in the conservative academic culture (Shannon 1999). Similarly, for their work, servant leadership scholars have sought a range of publication outlets while confronting a debate on the distinction and significance for organizations and employees of this leadership theory. Moreover, the acceleration of knowledge production in the field of management has resulted in a body of knowledge that is increasingly transdisciplinary, fragmented, and interdependent on progress in the social sciences. A literature review is a key tool for managing the diversity of knowledge for an academic investigation in management research; however, a criticism of these reviews is that they are typically descriptive accounts of contributions of selected writers often arbitrarily chosen by the researcher for inclusion and that these reviews may lack a critical evaluation of included studies (Tranfield et al. 2003). On the other hand, a SLR differs from traditional narrative reviews by adopting a replicable, scientific and transparent process aimed at mitigating bias through comprehensive literature searches and providing an audit trail of the findings. A discussion of how to conduct an SLR, critically evaluate studies, and integrate the conclusions is a current management research gap. We assess the current state of the field in servant leadership research in this SLR and synthesize divergent studies. We also advance a rigorous methodology for conducting an SRL in management research in this SLR.
Therefore, the purpose of this study was to systematically examine and organize the current body of literature research that in a given organizational environment, either quantitatively or qualitatively explored servant leadership theory. We included only empirical studies in this SRL that examined servant leadership in an organizational context and excluded studies focusing primarily on model development or testing measurement tools. Previous reviews on the concept of servant leadership focused on: the identification of key features (Russell and Stone 2002), the development of measurements (Barbuto and Wheeler 2006), and the suggestion of a theoretical framework (Van Dierendonck 2011). While these reviews help provide insight into how researchers have attempted to operationalize servants' leadership, none of them have been done systematically (i.e., no methodology for selecting articles or limiting bias), and none of them have specifically investigated empirical research. This SLR was guided by the following research questions: (a) How has servant leadership been defined? (b) Servant Leadership Theory Empirically Investigated in What Contexts? Moreover, (c) How was Servant Leadership (i.e., Methodology) reviewed? We begin this paper by summarizing servant leadership's origin and following the development of servant leadership as a theory and a new field of research with a brief discussion. Next, a summary of the method used to select and review the literature, with details of the search strategy, analysis, and quality assessment of the studies reviewed, is explained. Then, on empirical studies that have explored servant leadership theory, we present our SLR findings. Furthermore, as an efficient technique for thematically mapping and holistically viewing new research topics, we discuss the methodological construction of conducting SLRs in management. By offering suggestions for future research and practice, we conclude.

SERVANT LEADERSHIP THEORY
Although servant leadership is a growing trend in the practice of private and non-profit organizations, there is still a lack of research in this area (Farling et al. 1999). The majority of servant leadership research streams from Greenleaf's (1977) foundational texts and the Greenleaf Center (see Akuchie 1993;Lopez 1995;McCollum 1995;Vanourek 1995). Many authors present narrative examples of how servant leadership is being used in organizations; however, this is also the primary limitation of much of the servant leadership literature (Bowman 1997;Northouse 1997;Sendjaya and Sarros 2002). Bass (2000) found that servant leadership requires extensive research, and that untested theories will play a role in the future leadership of the learning organization (p. 33). The servant-first paradigm has since motivated scholars and practitioners to explore the possibilities of this paradigm.
As of 1999, two research streams had emerged: conceptual (Spears, 1998;Patterson, 2003), measurement (Page and Wong, 2000;Van Dierendonck and Nuijte, 2011). Notably absent are empirical studies exploring servant leadership theory in a given organizational setting. Although growing research has been done, it is still underdefined, and authors struggle to agree on what it means (Anderson 2009). Greenleaf (1977) noted that command and control leadership would be difficult to apply and operationalize. He challenged readers to ponder, contemplate, and reflect (Frick 2004;Spears 1995).
The three reviews provide insight into how researchers have organized the complexity of Greenleaf's concepts on servant leadership into a theoretical framework. Russell and Stone (2002) identified nine functional attributes of servant leaders, or operator qualities and distinctive characteristics. Russell and Stone included 11 core attributes and 11 additional attributes interrelated and supportive of the core attributes listed above. Russell and Stone's research on the attributes of leadership helped to guide future applications and research. However, they do not provide a complete analysis of leadership styles. After conducting a literature review, Barbuto and Wheeler (2006) developed an integrated servant leadership model that synthesized servant leadership attributes into five variables; altruistic calling, emotional healing, persuasive mapping, wisdom, and organizational stewardship. Van Dierendonck's (2011) third review also concludes with another conceptual model that identifies six key features of leadership: empowering and developing individuals, humility, authenticity, interpersonal acceptance, guidance and stewardship. All of these reviews exemplify various interpretations of Greenleaf's writings using various terminologies; all, however, include the fundamental mental dimension of servitude or the willingness to serve others. These reviews emphasize the plurality of the theory of ser-vant leadership, allowing the researcher, student, or practitioner to ponder precisely the theory of servant leadership. There is more than one kind of good theory, as DiMaggio (1995) pointed out (p. 391).
Since the development of conceptual frameworks and measurement tools for servant leadership has been examined in previous reviews, the present review focuses only on empirical studies that have explored the theory of servant leadership in an organizational context. As such, the current study is the first review to provide a synthesis of empirical studies conducted on the theory of servant leadership in organic settings, based on evidence in published peer-reviewed journals.

METHOD
The SLR is often compared to traditional reviews of literature because systematic reviews are objective, replicable, systematic, comprehensive, and the method is reported in the same way as empirical research reporting (Weed 2005). The origin of SLRs is in the fields of medicine, health care and policy, where the best evidence has been used to make clinical and policy decisions (Cook et al. 1997;Tranfield et al. 2003). Management SLRs are used to provide a specific area with transparency, clarity, accessibility and impartial, inclusive coverage (Thorpe et al. 2006). SLR is defined by Klassen et al. (1998) as " a review in which there is a thorough search for relevant studies on a particular subject, and those identified are then evaluated and synthesized according to a pre-determined explicit method " (p. 700). This SRL has specifically examined studies that have examined the theory of servant leadership in a given organizational environment. Since our focus was to gain insight into the empirical study of the theory of servant leadership, studies with a primary focus on model development or testing of measurement tools were excluded. The approach of this review included extensive searches of relevant databases in order to ensure that all literature on servant leadership was identified as far as possible while maintaining the focus on literature that is most relevant to research issues (i.e., empirical studies that have investigated servant leadership theory in organizational settings). Next, our search methods, criteria for inclusion and exclusion, sample and data analysis are discussed.

Methods of Search
Published studies have been identified by searches of electronic databases accessible via the authors' university library system. The databases included in this study were: PsycInfo, Eric, Sociological Abstracts, PAIS Inter-national, Social Services, Communication Abstracts, International Social Sciences Bibliography (IBSS), Physical Education Index, Vendor CSA World Wide Political Abstracts, Academic Search Complete, Business Source Complete, Communication, and Mass Media Complete, Education and Administration All results were restricted to peer-reviewed journal articles in English only. Searches for pub-led studies were carried out systematically, following the order of the above-mentioned databases.

Criteria for inclusion and Exclusion
The initial search required studies that must: (a) be published in a peer-reviewed journal; (b) be in the English language, and (c) use the keyword " servant leadership." No restriction was placed on the year of publication. The number of articles recovered from each database containing the keyword " servant leadership " was recorded. Next, we examined whether any external duplicates were being searched from the current database and from the previous databases that were already searched. The number of external duplicates was recorded, and then duplicated journal articles were deleted from the last searched database while keeping the total number of new articles found running.
Once all possible studies were identified, a second screening was conducted to evaluate eligibility for inclusion criteria, and then full-text papers were retrieved for those who met the inclusion criteria. The inclusion criteria for the second screening required that the published peer-reviewed article meet all the following four specifications: (a) be in the English language; (b) be an empirical study (i.e., not an essay, book review, letter, literature review, editorial, opinion, journalistic or antidote article); (c) discuss servant leadership as the main topic; and (d) discuss servant leadership as the main topic; Articles were excluded where the abstract, results or discussion sections of the respective study did not address any of these four components. Finally, by examining the bibliographies of resources identified through the secondary screening, additional articles satisfying the inclusion criteria were found.

Sample
Using the key terms outlined in the inclusion and exclusion criteria section above, peerreviewed publications were identified. In all, a total of 381 articles were retrieved; however, there remained 255 articles meeting the initial inclusion criteria after duplicates were deleted. A

International Journal of Educational Administration, Management, and Leadership
Volume 1, Number 2, November 2020, Page 63-76 final sample of 44 appropriate studies was obtained after the secondary search process was performed. Upon retrieving full-text articles, an additional five articles were excluded after the further examination because they did not meet the screening criteria. Thirty-nine empirical studies formed the final sample of articles. Between 2004 and 2011, peer-reviewed articles meeting the outlined criteria were published. The 39 published articles were drawn from a variety of peer-reviewed journals (n = 27). The list of journals included in the study, the number of articles from each journal included, and the database they accessed are shown in Table 1.

Data Analysis
As the strategy for organizing and abstracting relevant information from these publications, the Matrix Method (Garrard 1999) was used. The following information from each article was abstracted for this study: (a) How was servant leadership defined? (b) In what circumstances was the theory of servant leadership empirically investigated? (c) How was servant leadership examined? Moreover, (d) What were the examination results? Last, the methodology used to examine servant leadership was assessed for each publication. We used a critical assessment instrument designed by Letts et al. (2007) for qualitative studies, and we used a critical assessment instrument designed by the Institute for Public Health Sciences for quantitative studies (2002). We used Stoltz et al. (2004) .'s critical evaluation tool in addition to these two evaluation evaluations, which evaluated both quantitative and qualitative studies. To create a three-point scale to reflect the quality of the studies, we adopted these three critical assessment tools: high (I); medium (II)-used if studies did not meet high (I) or low-quality criteria; and low (III). Our classification for high to low-quality studies is described in Table 2, which was based on the three critical assessment tools listed above.
The results of these studies have been summarized and put into matrices. Our SLR findings consist of a synthesis of the results for each study from all 39 empirical studies along with the quality assessment. In addition, we evaluate the degree of supporting evidence for the-matic conclusions drawn from combining the findings of several studies.

RESULT AND DISCUSSION
Overall, this review highlights that the theory of servant leadership is being studied and tested across a range of contexts, cultures, disciplines, and themes. 11 qualitative studies, 27 quantitative studies, and one mixed-method study were included in our sample, all empirically evaluating the theory of servant leadership. Therefore, this review shows that servant leadership is being studied both quantitatively and qualitatively, and with studies being conducted in 11 countries, the subject has an international appeal. 22 studies were classified as high, 12 as medium, and five as low quality in the quality evaluation. Based on the synthesis of findings from each article, conclusive statements were made. Based on scientific strength, the conclusions (see Table 3) were classified as A (strong evidence) or B (moderate evidence).
Where two or more high-quality studies supported a conclusion or one high-quality study in addition to two or more medium-quality studies supported the conclusion, we assigned a (A) rating to it. On the other hand, one high-quality study's conclusions and one medium-quality study or two medium-quality studies were assigned a (B) rating. If it did not fall under a conclusion(s) We have classified (a) strong evidence in favor of conclusion or (b) moderate evidence in favor of conclusion as inadequately supported and labeled as inadequate evidence. The following discussion of our findings is organized around the four central research questions.

How has Servant Leadership been defined?
Servant Leadership Theory was introduced to readers by authors of empiric studies, citing one or all three of the following: Greenleaf (1977), Spears (1995, 1998), and Laub (1999. In general, the authors described the servant-leader by quoting one of these three authors, not to mention several other authors, including, but not limited to: Barbuto and Wheeler (2006), Graham (1991), Ehrhart (2004), Liden et al. (2008), Page and Wong (2000), and Patterson (2003). Here, we discuss the three most-cited authors on the leadership of servants who have provided definitions. Greenleaf (1970Greenleaf ( , 1972aGreenleaf ( , b, 1977, the grandfather of servant leadership, was cited in 37 of the 39 empiric studies. Most of the authors used part or all of Greenleaf's description of his original essay, The Servant Leader (1970): It begins with the natural feeling that one wants to serve, to serve first. Then a conscious choice brings one to aspire to lead. That person is distinctly different from the leader first.
The difference manifests itself in the servant's care-first to make sure that other people's highest priority needs are being served. The best test, and difficult to manage, is this: are those served growing up as individuals? Do they become healthier, wiser, freer, more autonomous, more likely to become servants while they are served? And what is the effect on society's least privileged? Will they benefit from it or at least not be further deprived of it? (Greenleaf 1970, cited in Greenleaf 1977.
Like Greenleaf himself, most authors in our sample defined servant leadership theory in a descriptive manner. These descriptions usually include several scholarly works in the conceptual and measurement research streams and the reference to leading authors of organizational management.
Larry Spears was the second best-referred author to define servant leadership theory. Like Greenleaf, Spears gained his knowledge from practice, most of his works being non-empirical. He served for 17 years as head of the Greenleaf Center, wrote more than 10 books on servant leadership, and established the Larry C. Spears Center for Servant Leadership, Inc. in 2008(Spears Center 2011. Spears (1995Spears ( , 1998Spears ( , 2004 identified 10 isthics of Greenleaf's servants' writings: listening, compassion, healing, awareness, persuasion, philosophy, conceptualization, foresight, stewardship, commitment to human growth, and community building. Four of the qualitative studies in our sample used Spear's 10 characteristics to inform their analysis (Crippen 2004;Crippen and Wallin 2008a, b;Sturm 2009). Laub (1999) is the third most cited author in defining the servant leadership theory. His Organizational Leadership Assessment (OLA) was the result of his dissertation. The OLA assesses the health of the organization on the basis of the six key areas of an effective service-oriented organization by exploring the perceptions of top leaders, managers and supervisors, and the workforce; however, it does not assess the leadership of the individual leaders (OLA Group 2011). Authors in our sample used Laub's definition, which refers to the practice of servant leadership as "the good of those led over the self-interest of the leader" (1999, p. 81). In addition, the authors would list and describe Laub's six key variables of effective servant-led organization: (a) values people-belief, service, and non-judgmental listening to others; (b) develops people-provides learning, growth, encouragement, and assertiveness; (c) builds a community-develops strong collaborative and personal relationships; (d) displays authenticity-be open; OLA has been widely used in health organizations (OLA Group) and has been used in six quantitative studies in our sample (Herman 2010;Black 2010;Cerit 2010;Cerit 2009;Irving and Longbotham 2007;Joseph and Winston 2005).
In summary, our results confirm Anderson's (2009) and Van Dierendonck's (2011) assessments that the servant's leadership theory remains under-defined, with no consensus on its definition or theoretical framework. Scholars are still trying to articulate Greenleaf's conceptualization of servant leadership by using various definitions from multiple works.

Servant Leadership Theory Empirically Investigated in What Contexts?
Our sample demonstrates the theory of servant leadership that is being studied across cultures, contexts, and a variety of research areas. Overall, the sample consisted of studies that included four cross-cultural studies in 11 countries. These results show that servant leadership is practiced in different cultures, specifically: the United States (n = 23), Canada (n = 4), China (n = 2), Turkey (n = 2), Indonesia (n = 1), New Zealand (n = 1), Kenya (n = 1), and the Republic of Trinidad (n = 1), with five cross-cultural studies comparing the United States and Ghana, the United States and the United Kingdom, the United States and China (n = 2), and Indonesia and Australia.
A contextual analysis of the sample revealed that the theory of servant leadership is applied in the following organizational environments: education (n = 17), consisting of religious schools (n = 6) and secular schools (n = 11); secular profit organizations (n = 17), including financial services (n = 4) and nursing (n = 3) in particular; public organizations (n = 2); religious organizations (n = 2) It is important to note that in seven of the 39 studies, servant leadership was examined in a religious context and that the field of education represents 44 percent of the contextual environment for the whole sample.

How was Servant Leadership (i.e., Methodology) reviewed?
The surveys were used as the data collection method in all 27 quantitative studies. Laub's (1999) OLA instrument-used in six studies (Herman 2010;Black 2010;Cerit 2009Cerit , 2010Irving and Longbotham 2007;Joseph and Winston 2005) and the Ehrhart Servant Leadership Scale (2004)-used in six studies-was the two most popular measures of the Servant Leadership Theory used in these empiric studies (Ehrhart 2004;Jaramillo et al. 2009a, b;Mayer et al. 2008;Neubert et al. 2008;Walumbwa et al. 2010). Responding to any issue automatically by listening receptively to what is said, which allows them to recognize the group's will and help clarify that will Empathy Striving to accept and understand others, never rejecting them, but sometimes refusing to recognize their performance as being good enough. Healing Recognizing them as human beings have the chance to make themselves and others' whole' Awareness Strengthened by general awareness and above all by self-awareness, which allows them to holistically view situations Persuasion Relying primarily on persuasion instead of coercion Conceptualization Seeking to awaken and nurture the capacity of theirs and others to 'dream great dreams' Foresight Understanding intuitively the lessons of the past, the realities of the present and the likely outcome of a decision for the future Stewardship Commitment to serving other needs first and foremost Commitment to the growth of people Nurtures each individual's personal, professional, and spiritual growth Building community Responding to any issue automatically by listening receptively to what is said, which allows them to recognize the group's will and help clarify that will Instruments used in two studies included: Barbuto and Wheeler's (2006) instrument (Jenkins and Stewart 2010; Garber et al. 2009); Liden et al. (2008). Instrument (Hu and Liden 2011;Schaubroeck et al. 2011);and Sendjaya et al. (2008) .'s survey Sendjaya and Pekerti 2010). Taylor et al. (2007) used Page and Wong (1998) self-assessment measures. Washington et al. (2006) the adopted version of Page and Wong's (2000). Rieke et al. (2008) used the Hammermeister et al. (2008) instrument. Babakus et al. (2011) and Hale and Fields (2007) used lesser-known scales, Lytle et al. (1998) and Dennis (2004) respectively. In summary, out of the 27 survey studies, 14 different measures were used. It is important to note that the majority of authors have combined multiple measurement scales to construct their surveys. In addition, the majority of these measures explored the theory of servant leadership at the unit level of analysis (i.e., group or team performance), while only a few examined it at the individual level of analysis (i.e., individual performance). Similarly, the 11 qualitative studies used various staff leadership frameworks to inform their analyses, while the three studies did not provide any framework information. Four of the qualitative studies used Spears (1998) 10 characteristics to inform their analyzes. Han et al. (2010) used multiple dimensions and definitions of service leadership in Western literature, including but not limited to: Barbuto and Wheeler (2006); Liden et al. (2008); Ehrhart (2004); and Sendjaya et al (2008). The multiple quantitative and qualitative measures used in the studies in our sample reinforce our findings for research question one, where it has been found that the authors have defined the leadership 72 International Journal of Educational Administration, Management, and Leadership Volume 1, Number 2, November 2020,  of the staff in a variety of ways. Similarly, as this review shows, there is still no agreement on a strategy to measure the theory of servant leadership.

CONCLUSION
This SLR demonstrates that the theory of servant leadership applies in a variety of cultures, contexts, and organizational environments. Although Greenleaf first coined the philosophy in the 1970s, it took until 2004 to explore servant leadership in an empirical way. No limitation was placed on the publication year of peer-reviewed journal articles by this SLR; however, no empirical studies were found in all databases searched prior to 2004. To date, the majority of servant leadership research is either attempting to define and model the theory conceptually or developing measurement tools to empirically test it. Thus, one of the major criticisms of the theoretical construct, which is the difficulty of operationalizing its concepts and principles, is addressed by the majority of research on servant leadership.
From our SLR, several interesting directions for future research have emerged. First, only 39 empirical studies that explored the theory of servant leadership in organic settings were identified by this SLR, highlighting the need for researchers to empirically examine the construction of servant leadership in a variety of organizational contexts. Researchers could explore how to build a servant-led organization in the burgeoning field of entrepreneurship or, in the area of organic change, research could explore how to implement servant leadership in an established organization or during a merger or acquisition. Second, there is a need to invest in the history of servant leadership development, such as the leader's personal attributes, the leader's background, and the history and trajectory of the organization.