Servant Leadership: Theory, Measures, and Nomological Network

Introduction

Evolutionary leadership biology indicates that humans evolve over long periods, and many needs of the hunter-gatherer within people remain unfulfilled. Leaders in hunter-gatherer tribes were known intimately by their tribesmen; hence there was no distinction between the public and private life of a leader. Today, large bureaucratic organizations with mobile employees dispersed worldwide have essentially embedded the small, family-like hunter-gatherer tribe structure into modern institutions (Babakus, Yavas, & Ashill, 2010). However, the modern organization has largely failed to provide employees with the sense of tribal belonging that the human mind requires. Servant leadership has emerged to fill this significant gap. It gives followers a sense of social identity and creates kinship-like teams similar to those found in hunter-gatherer societies. Team members help and develop each other's capacity.

Servant leadership can deliver leadership capable of solving most modern workplace challenges while providing humans with a hunter-gatherer sense of belonging. This explains why organizations such as Southwest Airlines and Starbucks continue to grow, and why servant leadership research is increasingly called for. Servant leadership is based on a holistic approach that engages the ethical, relational, spiritual, emotional, and other dimensions of leadership followers (Babakus, Yavas, & Ashill, 2010). The leadership approach empowers followers to grow to their maximum potential, first by allowing them to develop based on their leaders' ethical and altruistic orientations.

Servant leadership prioritizes followers' growth and general well-being, making them more effective and engaged in their specific work (Babakus, Yavas, & Ashill, 2010). As organizational stewards, servant leaders are determined to grow the finances and resources of the company entrusted to them. Therefore, servant leaders emphasize their followers' personal development without overlooking organizational performance expectations. Unlike leadership approaches based purely on performance, servant leadership focuses on long-term sustainable performance. Performance-based leadership approaches tend to promote organizational growth and profit at the expense of people.

Servant leadership research is grouped into three stages: conceptual development, measurement, and analysis of servant leadership against outcomes (Babakus, Yavas, & Ashill, 2010). The third stage — model development — involves complex research designs that examine not only essential servant leadership relationships with outcomes but also mediating mechanisms, antecedents, and boundary conditions. Since Graham's (1991) foundational research on servant leadership theory development, research has theoretically and empirically differentiated servant leadership from other leadership approaches. The lack of clarity and coherence in the subject, despite surging academic interest, also informs the purpose of this research.

Research on servant leadership has been conducted across multiple disciplines, including management, education, nursing, youth work, tourism, public administration, and not-for-profit sectors, appearing in their respective journals. Decades of multi-disciplinary research have advanced servant leadership theory, but the fragmented studies have not been integrated (Babakus, Yavas, & Ashill, 2010). Existing measures of servant leadership have yet to be thoroughly assessed. This paper evaluates those measures to form a basis for future research. It also reviews servant leadership in relation to outcomes, discusses the positioning of servant leadership within the leadership theories network, and provides a clear definition of the construct. Additionally, the paper evaluates empirical servant leadership work to map the nomological network based on antecedents, theories, outcomes, and construct mechanisms, before discussing limitations, implications, and suggestions for future empirical and theoretical advancement.

Although the number of leadership theories continues to grow, no consistent evidence demonstrates that each new theory empirically and theoretically differs from its predecessors. Some studies have provided empirical evidence to support the rising validity of servant leadership over other forms of leadership (Barbuto Jr., Gottfredson, & Searle, 2014). However, limitations in existing research — including measurement error, endogeneity bias, common method bias, relatively low sample sizes in meta-analyses, and a small number of available studies — make this difficult to confirm. Empirical and theoretical arguments nonetheless showcase how servant leadership differs from ethical, transformational, and authentic leadership.

Understanding and Defining Servant Leadership

Servant leadership's conceptual separation from other approaches addresses the problem of unjustified categorization. It eliminates the incorrect assumption that servant leadership is simply another value-based leadership technique (Barbuto Jr., Gottfredson, & Searle, 2014). Servant leadership differs conceptually from transformational leadership in that it focuses more on followers' psychological needs as a goal in itself. By contrast, transformational leadership treats those needs as less critical relative to the goals of the organization.

A common overlap between the two types of leadership is that both emphasize the needs of followers. However, they differ qualitatively in terms of why that focus is emphasized and how it is positioned relative to other key organizational factors. Transformational leadership emphasizes follower needs primarily as a means of helping the organization attain its objectives more effectively — a means to an end. Servant leaders, by contrast, focus on followers' multidimensional development as an ultimate goal. When servant leaders address their followers' needs, the organization's goals are eventually met as a by-product of satisfying those needs over time (Barbuto Jr., Gottfredson, & Searle, 2014). Unlike transformational leaders, servant leaders are more likely to prioritize followers' needs first, followed by organizational needs, with their own needs fulfilled last.

Servant leadership, like authentic leadership, acknowledges the importance of being genuine when interacting with others in the organization. However, the servant leader's need to work from a deep sense of self-control and self-awareness stems from an altruistic and spiritual motivation to serve followers — an element not present in authentic leadership. Servant leaders are motivated by an inner conviction or higher calling to be authentic, to serve others, and to make a meaningful difference in their lives (Barbuto Jr., Gottfredson, & Searle, 2014). Compared to ethical leadership, servant leadership adopts stewardship as a central element of effective leadership, with a long-term focus encompassing all stakeholders.

According to ethical leadership theory, a leader's behavior is more prescriptive and rule-governed, aligned with what the leader's innate ethical principles deem appropriate. Servant leaders' behavior, by contrast, is more contingent and flexible, balancing the needs of both the organization and followers. Ethical leadership emphasizes trustworthiness, honesty, and care for people, but places relatively little emphasis on directing followers or on authenticity. Servant leadership, unlike transformational leadership, can also predict follower outcomes with greater precision (Barbuto Jr., Gottfredson, & Searle, 2014), offering up to 12% greater incremental variance on follower outcomes than transformational approaches. Ethical leadership offers an outcome variance of 6.2%, and authentic leadership 5.2%.

Further research is needed to differentiate servant leadership empirically from other leadership forms. Researchers must use more robust techniques to analyze how servant leadership differs empirically from other theories, and there is also a need to determine servant leadership's predictive or incremental validity over competing theories (Barbuto Jr., Gottfredson, & Searle, 2014).

A servant leader has the natural inclination to serve followers first. The leader is a servant before becoming a leader, and the choice to lead is made consciously. Servant leadership is an approach oriented toward others — it involves a leader prioritizing the interests and needs of individual followers and reorienting personal concerns toward others within the same organization or community (Barnes et al., 2015). The motive of servant leadership is the "servant-first" element that originates outside the leader's self-interest, hence the other-oriented approach. Unlike other leadership approaches, the servant leader is motivated from within to take up leadership roles. This orientation to serve others reflects the leader's conviction and belief that leading followers is a path away from self-orientation.

Other leadership approaches, by contrast, tend to emphasize leaders advancing their own agenda or ambition. A servant leader's self-concept as a moral, altruistic person drives their resolve to serve their followers. A servant leader is not necessarily friendly or courteous in a superficial sense but has a strong sense of character, self, and psychological maturity (Barnes et al., 2015). Anyone unwilling to serve others is not suited to become a servant leader. Servant leadership recognizes that every follower is unique and has distinct interests, needs, goals, desires, limitations, and strengths. The relationship between a leader and followers takes varying forms despite organizational systems and policies designed to ensure equity. This is the servant leadership model that places others before self.

Servant leadership involves understanding the core values, background, assumptions, beliefs, and characteristic behaviors of followers, at times blurring the line between a leader's personal and professional life. Unlike other leadership approaches, servant leaders aim to help followers grow in multiple areas, including emotional maturity, psychological well-being, and ethical wisdom (Barnes et al., 2015). Other leadership approaches focus primarily on advancing the organization's bottom line. The focus of servant leadership aligns with stewardship — the servant leader is responsible for helping individual followers reach greater heights and better themselves. In turn, followers come to regard their servant leaders as trustworthy persons.

The servant leadership mindset reorients self-concern toward others within the same community or organization. The mindset is that of a trustee. The servant leader deliberately emphasizes the development of followers out of genuine concern for the larger organization or community, and is dedicated to being accountable for followers' general well-being. Servant leaders believe that the individuals among their followers have been entrusted to them for care — hence the notion of stewardship (Barnes et al., 2015). Servant leaders, as trustees, ensure that the organizational resources and followers entrusted to them develop and grow responsibly. By moving from self-serving to other-serving orientation, servant leadership empowers followers to be productive. These leaders are pro-social catalysts with the ability to positively impact the lives of others.

Servant leaders work to change broken social structures within their environment of operation. The motive, mode, and mindset aspects of servant leadership together provide a precise understanding of this form of leadership (Barnes et al., 2015). Whether focused on the spiritual, ethical, communal, or all aspects of servant leadership, it is clearly centered on others, involves personal interactions between followers and leaders, and includes an overarching concern for followers' general well-being. This paper's definition of servant leadership can inform future research in creating a more detailed and coherent servant leadership theory.

Approximately sixteen servant leadership research measures have been developed. The 7-item composite known as the Servant Leadership measure (SL-7) incorporates a servant leader's genuine and conscious concern to create value for both followers and the surrounding community. It includes how a servant leader encourages followers to actively participate in community activities (Butler Jr., 1991). The leader's community-oriented dimension is reflected in how they give back to the community. Moreover, the SL-7 includes a distinct dimension based on competencies such as conceptual skills and character. This measure is best suited for community-based outcome variables or competencies based on cognitive skills. As a global servant leadership measure, the SL-7 is straightforward to use alongside other measures because it contains only seven items.

Servant Leadership Measures and Research Design

The 6-item composite known as the Servant Leadership Behavior Scale (SLBS-6) maintains the factorial structure and hierarchical model of the original SLBS-35 measure at a higher order. The spiritual dimension of this measure differentiates it and renders servant leadership genuinely holistic. The inclusion of spirituality reflects early and subsequent theories stating that servant leadership depends on humility and spiritual insight as significant sources of influence (Butler Jr., 1991). The measure is ideal for studies focusing on the spiritual dimension of servant leadership. Like SL-7, SLBS-6 is short and easy to employ. Both measures deliver consistent psychometric properties and accurately capture the essence of the full measures, making them ideal for global or general servant leadership studies.

The complete scales — SLBS-35 and SL-28 — are suited for separately assessing individual dimensions of servant leadership to determine their reliability and improve validity. Shorter measures are not ideal for dimensional analysis. The 30-item Servant Leadership Survey (SLS) is appropriate for this purpose (Butler Jr., 1991). It features 30 items representing eight servant leadership dimensions: forgiveness, standing back, empowerment, courage, authenticity, stewardship, accountability, and humility. It is longer than the first two measures and considers the relationship between the "leader-side" and "servant-side" of servant leadership.

The model embedded in the SLS demonstrates that servant leaders empower people and help them develop while holding them accountable for their work outcomes. It shows that servant leaders are open to learning, humble, and willing to acknowledge their mistakes. They also stand for their core values and emphasize the common good of everyone in the organization. A shorter, 18-item version of this measure demonstrates cross-cultural factorial stability (Butler Jr., 1991). Servant leadership measures inherently emphasize the leader-follower hierarchical dyad. However, alternate structures have emerged, resulting in non-traditional leadership scenarios. A notable example is the adoption of shared leadership in medicine, education, and volunteer or not-for-profit organizations.

Existing servant leadership measures can be restructured to reflect shared leadership in a reliable and valid way. For example, a 15-item shared measure can be derived from the 30-item SLS by shifting from rating the servant leader to rating other team members, retaining only team-member items rather than leader-follower items. The servant leadership measure can also be adapted to accurately capture distinct scenarios or settings, such as non-traditional leadership forms (Butler Jr., 1991). Referent-shift consensus models and re-validated servant leadership measures are suitable for confirmatory or exploratory factor analysis. Irrelevant items may be dropped after appropriate psychometric re-analyses. SL-7, SLBS-6, and SLS are the most recommended servant leadership measures overall.

The qualitative servant leadership research design makes use of focus groups, interviews, and observations. These data collection methods are straightforward to use and analyze (Creswell & Clark, 2017). Interviews allow researchers to collect data from small subject groups on a wide range of topics including servant leadership. Structured interviews — featuring predetermined questions with multiple-choice responses — keep the data collection process focused, depending on the researcher's skill level. The interviewer maintains control of the process, keeping interviewees on track and ensuring all questions receive responses (Creswell & Clark, 2017).

Interviews help researchers obtain detailed information about study respondents' perceptions, feelings, and opinions (Creswell & Clark, 2017). They deliver a high response rate, allow more detailed questions, and capture respondents' exact words — all of which contribute to reliability and accuracy. Primary data sources were mainly used for data collection in this study. They are specific, authentic, and provide up-to-date information. Although primary data is more costly and time-consuming to gather than secondary data, objective data collected directly from its source is inherently more reliable.

The research also sought to determine how servant leadership manifests within organizations while being informed by relevant theories (Ehrhart, 1998). Mixed-method research designs — combining organizational surveys with follow-up interviews — can help researchers understand the servant leadership phenomenon more fully. There is a need for more servant leadership studies to be theoretically grounded. Servant leaders and their followers in different organizations and work settings were interviewed to provide accurate information for this research.

Conclusion

Practitioners need to understand that servant leadership's impact on organizational outcomes is typically indirect. Leaders are empowered to focus on providing followers with what they need to reach their full potential, while also handling personal decisions and tasks individually. Servant leaders cultivate a culture of serving others and communal sharing (Greenleaf, 1977), which in turn encourages employees to serve customers effectively. Customer satisfaction, promotive voice, and repeat purchases generate organizational loyalty, driving higher stock prices and revenue growth. Beyond recognizing these benefits, practitioners must also prepare for the significant effort required to build a servant leadership culture, beginning with servant leaders themselves as role models.

When leaders prioritize meeting followers' needs, they must actively counter human survival instincts driven by self-interest. Servant leaders require discipline to manage these instincts within themselves through role modeling, and to reduce them within their employees through encouragement and support. Because servant leadership is difficult to master, it requires ongoing and deliberate practice to maintain its orientation. The resulting benefits — particularly the development of strong mutual trust between servant leaders and their employees — make servant leadership a worthwhile investment for organizations. Employees are inspired to develop behaviors that benefit customers, their colleagues, and the organization as a whole (Greenleaf, 1977).

Developing a servant leadership culture requires both selecting conscientious, socially motivated people and offering targeted servant leadership training. The extent to which training can alter stable personality traits places a premium on sound selection practices. For example, dogmatic, self-centered, or narcissistic individuals are difficult to train into empathetic, other-centered servant leaders regardless of the training program's quality. Furthermore, like any organizational change, transitioning a company from a command-and-control culture to one centered on servant leadership may take several years (Greenleaf, 1977). Organizations pursuing this cultural shift must exercise patience to enjoy its long-term benefits.

Future servant leadership research on advancing theoretical frameworks is encouraging, but existing gaps require further study. Alternative theoretical perspectives — including situational strength, conservation of resources, and self-determination theories — can improve understanding of how servant leadership affects teams, followers, and organizations (Greenleaf, 2009). A methodological roadmap is also needed to support the field. Over-dependence on single-respondent, cross-sectional survey designs is impeding progress. Research questions paired with corresponding alternative methodological strategies can evaluate and confirm existing knowledge on servant leadership in more rigorous ways.

Future studies should ensure that servant leadership outcome findings are actionable as evidence-based practices valuable to business and health practitioners, rather than simply adding more variables to the current nomological network (Greenleaf, 2009). Practical, evidence-based implications must be built into the general objective of any study, not treated as an afterthought. For instance, when introducing new mediators into the nomological network, studies must integrate existing mediators of the leader-follower relationship to demonstrate the new mediator's incremental variance.

Researchers must also use more robust techniques to analyze how servant leadership differs empirically from other leadership theories, and further work is needed to determine servant leadership's predictive or incremental validity over competing theories (Greenleaf, 2009). Future studies should assess the relationship between a leader's sex, age, tenure, and education and servant leadership behaviors to develop a more holistic picture of leadership and demographics. Future research should also systematically include and report insignificant findings, include competing mediators in research designs, and apply the COR, situational strength, and SDT theories to extend the servant leadership theoretical framework and widen the nomological network for new empirical avenues (Greenleaf, 2009).

Additionally, the self-determination theory should be more thoroughly integrated into servant leadership antecedent research, while the situational strength theory can help address unresolved questions about boundary conditions (Akbari et al., 2014). Mixed-method designs pairing interviews and ESM — with qualitative findings prioritized during data interpretation — can address the missing explanatory layer in current survey-based research. Data should be collected simultaneously from multiple time points to eliminate common method bias, and future studies should include multiple competing variables to more accurately reflect servant leadership's true effects.

There is an increased and growing interest in servant leadership research. This paper discussed how servant leadership is understood in the existing literature and provided a clear, comprehensive new definition of the construct. It reviewed various servant leadership measures and concluded that SL-7, SLBS-6, and SLS are the three measures most thoroughly evaluated for validation and construction rigor, making them the most recommended for research use. The paper analyzed and mapped the servant leadership nomological network, presenting the context of existing research studies, and detailed a research agenda for enhancing how servant leadership is studied in the field.

The research has demonstrated that the field of servant leadership has progressively advanced over the last two decades. However, it remains heavily critiqued. The empirical and conceptual overlap between servant leadership and ethical, transformational, and authentic leadership approaches remains a point of contention. Critics also argue that existing servant leadership research is constrained by its research design. Nevertheless, restarting the field would be premature, as most existing issues have arisen from poor measurement, insufficient construct clarity, and weak research design rather than from fundamental flaws in the construct itself. With the recommendations and suggestions for further study offered in this paper, it is anticipated that these issues can be resolved, allowing servant leadership research to continue generating significant insights and findings for the leadership field over the coming decades.

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