Transformational leadership effectiveness: an evidence-based primer

ABSTRACT

The proliferation of leadership models can leave practitioners confused about which model to use in guiding their leadership development initiatives. Although ‘new’ leadership models (e.g. authentic, ethical, and servant leadership) suggest theoretical differences, empirical research has shown considerable overlap among these models and longer standing ones such as transformational leadership. With extant literature questioning the added empirical value of these newer models, this paper aims to distil the best evidence about transformational leadership into a ‘primer’ that can help practitioners use evidence-led practices in their leadership development. To do so, we briefly review major leadership models, highlight evidence for empirical redundancy between new leadership models and transformational leadership, and discuss meta-analytic findings between transformational leadership and outcomes of leadership. Our review suggests that these newer leadership models add little incremental validity beyond transformational leadership in predicting various leadership outcomes. Moreover, transformational leadership demonstrates medium to large effect sizes on a range of individual, team, and organisational outcomes. Taken together, our findings suggest that organisations can benefit by focusing their resources on transformational leadership development, rather than on the latest leadership fad.

KEYWORDS:

• Leader development
• leadership development
• organisational development
• transformational leadership

Overview of leadership models and their outcomes

Leadership is a vital part of every organisation; it is often the cornerstone of organisational operations and the main driver of change. Determining which model of leadership is most helpful for developing leaders and achieving an organisation’s desired results is a complex endeavour. For this reason, decades of research have focused on defining and understanding effective leadership, resulting in a multitude of leadership models. Yet, as these models become increasingly nuanced with recent theoretical developments, navigating and applying them in practice can be extremely difficult.

Moreover, recent research has shown that new leadership models – ethical leadership (Brown, Treviño, and Harrison 2005), authentic leadership (Avolio and Gardner 2005), servant leadership (Barbuto and Wheeler 2006)—and transformational leadership are highly related empirically, suggesting considerable redundancy (Hoch et al. 2018). In other words, constructs proposed by new leadership models may not be as distinct from longstanding leadership models like transformational leadership (Banks et al. 2016, 2018; Hoch et al. 2018) as their conceptual unveilings might suggest. As such, there is concern about construct proliferation (i.e. the abundance of models with different names that tap into the same idea [Le et al. 2010]) in the field of leadership (Bormann and Rowold 2018). Construct proliferation has negative implications for both research and practice. From a research perspective, when a field proposes several new theoretically distinct constructs to describe a similar idea, there is greater risk that constructs may be highly related (i.e. tap into the same thing) and may also share similar patterns of relationships with other variables (Le et al. 2010). This risk, known as ‘construct empirical redundancy’, makes it harder to distinguish between constructs and their unique roles within a conceptual network (Le et al. 2010).

The lack of clarity from research can also translate into practical issues, as construct proliferation may lead human resource development (HRD) professionals to confusion about what model to use in their leadership development programmes. Such confusion can result in significant spending in unprofitable directions. Considering the limited resources that most organisations have, investing in a new programme with marginal value would be undesirable and ineffective. By some estimates, organisations spent $3.5 billion USD globally on leadership development initiatives in 2019 (Training Industry 2019). Judicious HRD professionals will therefore want a clear, evidence-based answer as to how these funds should be spent – that is, as to which leadership model will be most effective in generating the maximum value for their organisation. By informing professionals in this way, leadership theory that avoids construct proliferation may minimise leadership development ‘fads’ in practice, saving organisations time and money in addition to addressing longstanding calls (e.g. Pfeffer 1993) to mitigate construct redundancy in the weak paradigms of organisational research.

With new leadership models showing very high correlations with transformational leadership, we focus our review on the most studied leadership model of the last three decades (Barling 2014) to provide HRD professionals with an evidence-based ‘primer’ that distils the leadership research literature. Specifically, we examine the effectiveness of transformational leadership, one of the three main components of the full-range leadership model (along with transactional leadership and laissez-faire leadership; Avolio and Bass 2002). To do so, we draw on quantitative syntheses (i.e. meta-analyses, a statistical technique that quantitatively amalgamates results from multiple studies in a research topic by combining single effect sizes into a single aggregated estimate [(American Psychological Association (APA) n.d)]) of existing empirical research. The result is an aggregated understanding of current thinking that can help practitioners to better understand the strength of the relationships between leadership behaviours and various outcomes of leadership (e.g. performance, well-being), rather than relying on vagaries of individual cherry-picked studies.

The rest of this paper is divided into four parts. First, we provide a brief overview of leadership models and commonly studied outcomes. Second, we discuss the potential construct empirical redundancy among the leadership models. Third, we highlight the aggregated relationships between transformational leadership and its outcomes. Finally, we conclude by discussing the limitations and practical implications of this research.

Leadership models

Although almost every leadership researcher seems to propose a new or modified definition of the construct, leadership is generally operationalised in two ways: (1) leadership as a formal role or (2) leadership as a social influence (Yukl and Van Fleet 1992). Most of the leadership research focuses on the latter, which it aims to understand through operationalisation of leaders’ behaviours. Hence, although the dominant view of leadership in past decades was that leaders could be differentiated from non-leaders based on traits such as personality and intelligence (Antonakis et al. 2018), modern theories have now shifted to view leadership as socially influential behaviours (Yukl 2012).

Yet, even within behavioural models of leadership, there is an abundance of leadership models. As noted, one of the most empirically researched models is the full-range model of leadership (Avolio and Bass 2002), which is comprised of transformational leadership, transactional leadership, and laissez-faire leadership. Of these components, transformational leadership has received considerable research attention (Dinh et al. 2014) and consists of four central leadership behaviours: idealised influence, intellectual stimulation, individual consideration, and inspirational motivation. These behaviours aim to ‘transform and inspire followers to perform beyond expectations while transcending self-interest for the good of the organisation’ (Avolio, Walumbwa, and Weber 2009, 423). However, one critique of transformational leadership is that an explicit moral dimension is lacking (Hoch et al. 2018), which have led to the development of more nuanced models of leadership emphasising ethical and value-based behaviours (Dinh et al. 2014). These new leadership models – authentic, ethical, and servant leadership – have become increasingly popular in research (Dinh et al. 2014). For a list of the four popular leadership models included in our review, along with their descriptions, please see Table 1.

Table 1. Overview of leadership models covered in this review.

Leadership Model	Approach to leadership	Description	Dimensions
Transformational leadership (Bass and Avolio 1993)	Inspirational focus (Banks et al. 2018)	Behaviours that inspire, empower, and aim to develop others	1) Idealised influence: Leading by example, gaining followers’ loyalty and respect through moral and ethical behaviour 2) Inspirational motivation: Communication of and enthusiasm towards goals and future states 3) Intellectual stimulation: Bringing nonconforming, unique perspectives to problems that inspire follower thinking 4) Individual consideration: Focusing on developing and supporting each follower through coaching, mentoring, and consulting
Authentic leadership (Avolio and Gardner 2005)	Values or moral focus (Banks et al. 2018)	Behaviours that reflect leaders’ awareness of their values and transparent communication of those values	1) Self-awareness: Understanding of one’s own strengths and weaknesses as well as how one makes sense of the world 2) Balanced processing: Unprejudiced processing of information concerning subjects external to the individual and about themselves 3) Relational transparency: Being honest and portraying one’s true self in interactions with followers 4) Internalised moral perspective: Using one’s own moral compass to make decisions without external influence
Ethical leadership (Brown, Treviño, and Harrison 2005)	Values or moral focus (Banks et al. 2018)	Behaviours that exemplify and encourage being a moral person	1) Moral person: Modelling normatively appropriate behaviours for followers, such as trustworthiness and honesty 2) Moral manager: Encouraging the use of ethical behaviours by explicitly discussing with followers and using two-way communication in such discussions, thus giving followers voice
Servant leadership (Barbuto and Wheeler 2006)	Values or moral focus (Banks et al. 2018)	Taking a service orientation towards work	1) Altruistic calling: Desire to positively impact others 2) Emotional healing: Dedication to helping with recovery from trauma or hardship 3) Wisdom: Cognisance of surroundings and anticipation of outcomes 4) Persuasive mapping: Using mental frameworks and logical thought processes 5) Organisational stewardship: Using the organisation as an instrument of positive change through betterment of the community

Leadership outcomes

Extant leadership research has examined various objective outcomes (i.e. outcomes that can be measured or quantified such as performance on a task) and subjective outcomes (i.e. outcomes that cannot be directly measured such as follower satisfaction and psychological well-being) to demonstrate the impact of successful leadership. As such, an array of outcomes has been investigated in relation to leadership including effectiveness (e.g. leader effectiveness, performance), attitudes (e.g. commitment, well-being), behaviour (e.g. group processes), and cognitive outcomes (e.g. climate) (Hiller et al. 2011).

Are leadership models distinct from one another?

Although the literature describes authentic, ethical, and servant leadership as conceptually different, these theories are commonly underpinned by ethical/moral values-based behaviours (Banks et al. 2018; Dinh et al. 2014; Hoch et al. 2018). This approach to leadership appears to differ from transformational leadership’s approach of inspirational or change oriented leadership behaviours (Banks et al. 2018; DeRue et al. 2011); however, extant literature questions the extent to which these new leadership models are empirically distinct from transformational leadership. Banks’s et al. (2018) review of meta-analyses about leadership suggests that these newer leadership models fail to demonstrate their distinctiveness relative to traditional (e.g. transformational, transactional) leadership behaviours. Likewise, Hoch’s et al. (2018) meta-analysis shows high correlations between transformational leadership and authentic (ρ = .75), ethical (ρ = .70), and servant leadership (ρ = .52). For reference, an absolute value of .09 and lower is regarded as a small effect, an absolute value between .10 and .26 is regarded as a medium effect, and an absolute value of .27 and higher is regarded as a large effect (Bosco et al. 2015). These results suggest considerable construct empirical redundancies, with potential negative implications for practice; for instance, investing limited resources in creating multiple, unique leadership development initiatives around all these different leadership models could be redundant and time consuming.

Moreover, not only are these new leadership models highly correlated with transformational leadership, but they also explain little additional variance beyond transformational leadership in various outcomes related to behaviour (e.g. job performance), attitudes (e.g. job satisfaction, commitment), and relational perceptions (i.e. trust in supervisor, leader-member exchange) (Hoch et al. 2018). Before we discuss these empirical findings, it is worth explaining a few key terms and concepts to help make sense of the literature.

Total variance is the variability of a score that is due to a combination of explained variance and error variance. Explained variance in turn refers to when something explains part of the variance in something else, meaning it is responsible for the changes in score for the part of total variance that it accounts for. For instance, consider the leadership outcome of leader effectiveness. If a leadership behaviour explains 20% (out of the total 100%) of the variance in leader effectiveness, then individuals who engage in more of that leadership behaviour will be more effective leaders. In addition, error variance refers to the variability that is due to factors that are out of our control (e.g. measurement error), and is present in the many calculated variances, meaning numbers such as 10% variance explained are quite reasonable when discussing the impact of a specific construct.

The inclusion of extra predictors – factors that estimate or forecast values of an outcome variable – can help account for more explained variance. However, it is important to determine how much of the variance the predictor explains on its own. This amount is referred to as ‘incremental variance’, the unique contribution of a predictor in explaining the variability of scores in the outcome variable beyond other predictors. For example, a leadership behaviour may explain 5% of the variance in leader effectiveness, while another leadership behaviour may explain an additional 10% of the variance beyond the first predictor. Such information can provide insight on how much a predictor contributes to the outcome variable.

With this understanding established, we can consider the incremental variance explained by new leadership models versus transformational leadership using findings from Hoch’s et al. (2018) meta-analysis. For behavioural outcomes (e.g. job performance), transformational leadership explained between 5% and 8% of the variance for outcomes in this category, whereas the new leadership models explained between 1% and 3% of the variance in most of the outcomes in this category. In contrast, ethical leadership explained an additional 17% of the variance in employee deviance, and servant leadership explained an extra 9% in organisational citizenship behaviours. For attitudinal outcomes (e.g. job satisfaction, organisational commitment), transformational leadership explained between 18% and 23% of the variance for outcomes in this category. The newer models explained between 1% and 10% additional variance for attitudinal outcomes in this category, with servant leadership explaining an additional 15% of the variance in organisational commitment and an extra 26% of the variance in job satisfaction.

Further, transformational leadership explained 42% and 50% of the variance in trust in supervisor and leader-member exchange, respectively. In this category of outcomes related to relational perceptions, authentic and ethical leadership explained between 5% and 11% additional variance, while servant leadership explained an additional 19% of the variance in trust in supervisor. Taken together, it appears that for most of the outcomes explored in Hoch’s et al. (2018) meta-analysis, the new leadership models explained very little incremental variance beyond transformational leadership. In some instances, the new leadership models uniquely added to the prediction of some behavioural, attitudinal, and relational perception outcomes; however, many of the unique contributions are relatively small when compared to the large contribution from transformational leadership. Thus, in a practical sense, it is unclear whether the additional contributions from the new leadership models translate into noticeable changes in various individual, team, and organisational outcomes related to leadership. Overall, this evidence does not demonstrate strong support that newer models provide additional value over and above transformational leadership. As a result, we focus instead the remainder of this paper on reviewing the effectiveness of transformational leadership.

Transformational leadership and its outcomes

Transformational leadership has been found to have a positive impact on numerous important outcomes, of which performance is just one. Indeed, outcomes such as organisational citizenship behaviours, extra effort, employee or work engagement, trust in the manager, higher leader-member exchange (Hoch et al. 2018), psychological empowerment and identification with the leader (Koh, Lee, and Joshi 2019), follower motivation (Judge and Piccolo 2004), and many more offer benefits to both employees and the organisation. Table 2 summarises the results of several meta-analyses on transformational leadership with regards to its studied outcomes. Of these studied outcomes, Table 3 presents the definitions of nine commonly measured outcomes of leadership in the literature, which centre on effectiveness and performance (Hoch et al. 2018; Judge and Piccolo 2004), creativity and innovation (Koh, Lee, and Joshi 2019; Lee et al. 2020), satisfaction (Hoch et al. 2018), commitment (Hoch et al. 2018; Jackson, Meyer, and Wang 2013), and well-being (Harms et al. 2017; Montano et al. 2017). In the following sections, we highlight the meta-analytic relationships between transformational leadership and these nine commonly measured outcomes of leadership.

Table 2. Meta-analytic results regarding the outcomes of transformational leadership.

				95% Confidence Interval^c
Outcome	k	Correlation	Size	Lower	Upper	Source
Performance
Leader effectiveness	53	.79ρ	Large^b	.72	.85	Hoch et al. (2018)
Leader effectiveness	27	.64ρ	Large^b	Excluded 0		Judge and Piccolo (2004)
Perceived team effectiveness	25	.34^r	Large^b	.28	.39	Burke et al. (2006)
Employee job performance	74	.27ρ	Large^b	.24	.31	Hoch et al. (2018)
Leader job performance	13	.27ρ	Large^b	Excluded 0		Judge and Piccolo (2004)
Team productivity	6	.25^r	Medium^b	.15	.35	Burke et al. (2006)
Group/Organisational performance	41	.26ρ	Medium^b	Excluded 0		Judge and Piccolo (2004)
Individual
Overall OCB	36	.28ρ	Large^b	.20	.35	Hoch et al. (2018)
Deviance	10	−.23ρ	Medium^b	−.32	−.15	Hoch et al. (2018)
Engagement	14	.48ρ	Large^a	.35	.63	Hoch et al. (2018)
Job satisfaction	55	.42ρ	Large^a	.37	.47	Hoch et al. (2018)
Job satisfaction	18	.58ρ	Large^a	Excluded 0		Judge and Piccolo (2004)
Extra effort	22	.85ρ	Large^b	.73	.98	Hoch et al. (2018)
Follower motivation	16	.53ρ	Large^a	Excluded 0		Judge and Piccolo (2004)
Psychological empowerment	24	.49ρ	Large^a	.41	.56	Koh, Lee, and Joshi (2019)
Creativity/Innovation
Creativity	37	.33ρ	Large^b	.23	.43	Koh, Lee, and Joshi (2019)
Creativity	55	.31ρ	Large^b	.23	.33	Lee et al. (2020)
Creativity (self-rated)	21	.36ρ	Large^b	.23	.41	Lee et al. (2020)
Creativity (other-rated)	34	.27ρ	Large^b	.19	.30	Lee et al. (2020)
Creative identity	4	.37ρ	Large^b	.18	.57	Koh, Lee, and Joshi (2019)
Creative self-efficacy	9	.34ρ	Large^b	.18	.50	Koh, Lee, and Joshi (2019)
Intrinsic motivation for creativity	6	.42ρ	Large^b	.16	.68	Koh, Lee, and Joshi (2019)
Innovation	34	.29ρ	Large^b	.21	.31	Lee et al. (2020)
Innovation (self-rated)	19	.33ρ	Large^b	.23	.34	Lee et al. (2020)
Innovation (other-rated)	16	.26ρ	Medium^b	.14	.26	Lee et al. (2020)
Commitment
Organisational commitment	43	.43ρ	Large^a	.37	.50	Hoch et al. (2018)
Affective commitment	30	.42ρ	Large^a	.36	.48	Hoch et al. (2018)
Affective commitment	102	.45ρ	Large^a	.42	.47	Jackson, Meyer, and Wang (2013)
Normative commitment	29	.34ρ	Large^a	.28	.39	Jackson, Meyer, and Wang (2013)
Continuance commitment	27	−.004ρ	Small^a	−.06	.06	Jackson, Meyer, and Wang (2013)
Interpersonal
Trust in manager	23	.65ρ	Large^a	.56	.72	Hoch et al. (2018)
Leader-member exchange	20	.71ρ	Large^a	.63	.80	Hoch et al. (2018)
Satisfaction with supervisor	44	.80ρ	Large^a	.71	.89	Hoch et al. (2018)
Satisfaction with leader	23	.71 ρ	Large^a	Excluded 0		Judge and Piccolo (2004)
Identification with leader	12	.61ρ	Large^a	.51	.70	Koh, Lee, and Joshi (2019)
Team/Organisational
Innovation climate	18	.62ρ	Large^a	.50	.75	Koh, Lee, and Joshi (2019)
Team learning behaviour	13	.49ρ	Large^b	.40	.67	Koeslag-Kreunen et al. (2018)
Well-Being
Negative affective symptoms	25	−.19ρ	Medium^b	−.25	−.12	Montano et al. (2017)
Burnout	28	−.21ρ	Medium^b	−.26	−.16	Montano et al. (2017)
Overall burnout	25	−.32ρ	Large^b	−.36	−.28	Harms et al. (2017)
Burnout (depersonalisation)	11	−.23ρ	Medium^b	−.30	−.16	Harms et al. (2017)
Burnout (emotional exhaustion)	20	−.26ρ	Medium^b	−.28	−.24	Harms et al. (2017)
Burnout (LPA)	10	−.22ρ	Medium^b	−.26	−.18	Harms et al. (2017)
Stress	37	−.20ρ	Medium^b	−.24	−.16	Montano et al. (2017)
Stress	34	−.28ρ	Large^b	−.34	−.22	Harms et al. (2017)
Well-being	34	.31ρ	Large^b	.23	.40	Montano et al. (2017)
Psychological functioning	38	.26ρ	Medium^b	.19	.32	Montano et al. (2017)
Health complaints	6	−.23ρ	Medium^b	−.26	−.20	Montano et al. (2017)

Note. k = number of correlations/effect sizes used to determine the meta-analytic correlation, OCB = organisational citizenship behaviours, LPA = low personal accomplishment, ρ = corrected correlation, ^r = uncorrected Pearson correlation, ^a = Bosco et al. (2015) attitudes/evaluations and leadership effect size benchmarks (<.17 = small, .18–.33 = medium, >.34 = large), ^b = Bosco et al. (2015) aggregate effect size benchmarks (<.09 = small, .10–.26 = medium, > .27 = large). ^c = A confidence interval is a range of values within which we can be fairly certain the true value lies (i.e. 95% of the tests we do will come up with a value in this range). When the confidence interval does not include 0 or noted with the term “excluded 0” then the correlation/effect size is significant.

Table 3. Commonly measured outcomes of leadership.

Outcome	Definition
Leader effectiveness	A leader’s successful use of personal influence that results in achieving organisational objectives in a way that satisfies those involved (e.g. followers, stakeholders) (Cooper and Nirenberg 2004).
Job performance	The “behaviour or action that is relevant for the organisation’s goals and that can be scaled (measured) in terms of the level of proficiency (or contribution to goals) that is represented by a particular action or set of actions” (Campbell 1999, 402).
Group/Team performance	“The emergent phenomenon resulting from the goal-directed process whereby members draw from their individual and shared resources to display taskwork processes, team work processes, and integrated team-level processes to generate products and provide services” (Salas et al. 2008, 906).
Organisational performance	Encompasses three specific areas of firm outcomes: “(a) financial performance (profits, return on assets, return on investment, etc.); (b) product market performances (sales, market share, etc.); and (c) shareholder return (total shareholder return, economic value added, etc.)” (Richard et al. 2009, 722).
Creativity and innovation	Creativity refers to the cognitive and behavioural processes used when developing new ideas, while innovation refer to the processes applied when implementing new ideas (Hughes et al. 2018).
Job satisfaction	An evaluative state that expresses contentment with and positive feelings about one’s job (Judge and Kammeyer-Mueller 2012, 343).
Satisfaction with supervisor	An individual’s overall favourable (or unfavourable) attitude towards their supervisor (Dubinsky and Yammarino 1985).
Commitment	The magnitude that an individual identifies and is involved with an organisation (Mowday, Steers, and Porter 1979). Commitment includes three components: affective commitment (the emotional connection that employees feel to their organisation); normative commitment (the obligation an individual feels to remain with an organisation); and continuance commitment (the perceived cost to an individual for leaving) (Meyer and Allen 1991).
Well-being	Anything relating to an individual’s hedonic and eudaimonic experience (Sonnentag 2015) and/or physical health (Grant, Christianson, and Price 2007).

Effectiveness and performance

With respect to sub-components of transformational leadership, intellectual stimulation (corrected correlation =.60) and individual consideration (corrected correlation =.62) have both shown strong correlations with leader effectiveness (Lowe, Kroeck, and Sivasubramaniam 1996). Idealised influence and inspirational motivation, taken together to form a measure of charisma (see Bono and Judge 2004), similarly showed a strong correlation with leader effectiveness (corrected correlation =.71; Lowe, Kroeck, and Sivasubramaniam 1996). When examining the effects of transformational leadership behaviours on effectiveness outcomes, meta-analytic evidence show that transformational leadership was positively related to leader effectiveness (ρ = .79, Hoch et al. 2018; $\hat{p}$ = .64, Judge and Piccolo 2004), and one meta-analysis showed that transformational leadership behaviours accounted for 8.4% of the variance in leader effectiveness (DeRue et al. 2011). In terms of performance outcomes, transformational leadership is positively related to employee job performance (ρ = .27) and accounts for 7% of the variance in the same (Hoch et al. 2018), as well as being significantly correlated with group or organisational performance ($\hat{p}$ = .26) (Judge and Piccolo 2004). These findings further demonstrate transformational leadership’s significant role in leadership outcomes and provide a strong reason for continuing efforts to better understand how to encourage and develop it.

Creativity and innovation

In one meta-analysis, Lee et al. (2020) found that transformational leadership was related to both creativity and innovation. When transformational leadership was broken down into its four components, each behaviour was moderately related to creativity (meta-analytic correlations between .20 to .22), and each of these behaviours accounted for approximately similar proportions of the explained variance in creativity. For a more nuanced understanding of transformational leadership and creativity, Koh, Lee, and Joshi’s (2019) meta-analysis investigated transformational leadership and a range of outcomes related to creativity. The authors similarly observed a strong positive association with creativity (ρ = .33) as well as with creative identity (ρ = .37), creative self-efficacy (ρ = .34), and intrinsic motivation for creativity (ρ = .42). Additionally, transformational leadership was also found to have a positive association with innovation climate (ρ = .62).

Satisfaction and commitment

One common outcome examined in leadership research is follower satisfaction and organisational commitment. A meta-analysis conducted by Judge and Piccolo (2004) found that transformational leadership predicted followers’ job satisfaction and their satisfaction with their leader. Similarly, Hoch’s et al. (2018) meta-analysis found a strong and positive relation between transformational leadership and followers’ job satisfaction as well as followers’ satisfaction with their supervisor. With respect to commitment, Hoch’s et al. (2018) found that transformational leadership was positively related to both organisational commitment (ρ = .43) and affective commitment (ρ = .42), and accounted for 18% of the variance in both affective and organisational commitment among employees. Furthermore, Jackson, Meyer, and Wang’s (2013) meta-analysis explored the relationship between transformational leadership and affective commitment, normative commitment, and continuance commitment. As in Hoch’s et al. (2018) work, transformational leadership showed a positive correlation with affective commitment (ρ = .45) as well as with normative commitment (ρ = .34). However, transformational leadership was not significantly related to continuance commitment.

Well-being

Meta-analytic evidence indicates a relationship between leadership and various follower well-being outcomes (see Table 2). Montano et al. (2017) recently found positive relationships between transformational leadership and overall follower well-being (e.g. positive emotions and life satisfaction), and follower psychological functioning. Furthermore, transformational leadership was associated with decreased follower negative mental health state (i.e. burnout, stress, health complaints, and maladaptive affective symptoms such as anger, anxiety, depression, frustration) (Montano et al. 2017). Transformational leadership behaviours were also related to lower levels of follower stress and burnout (Harms et al. 2017). In sum, the existing meta-analytic evidence suggests that transformational leadership is related to enhanced follower well-being.

Discussion

In this paper, our goal was to organise the existing evidence on transformational leadership and its outcomes to create a primer for practitioners. To this end, we briefly reviewed popular leadership models, established the very high correlation among newer models of leadership (e.g. authentic, ethical, servant) and transformational leadership, highlighted the limited incremental validity of the new leadership models beyond transformational leadership, and then discussed the relationships between transformational leadership and a wide range of outcomes. As can be seen from the multitude of leadership models and the many important outcomes of leadership beyond effectiveness, leadership is a complex behaviour with far-reaching effects. Thus, figuring out the best way to increase the effectiveness of enacted leadership is vital for organisations and their members to excel.

Our review of the leadership research revealed that transformational leadership has a plethora of empirical evidence to support its effectiveness in terms of multiple objective and subjective leadership outcomes. The summaries of the meta-analytic evidence showed a medium to large effect size, which demonstrates a strong link between transformational leadership behaviours and various individual, team, and organisational outcomes. As such, the evidence reviewed in this paper suggests that leaders who engage in more transformational leadership behaviours are likely to be more effective leaders. Moreover, followers of transformational leaders are also likely to have higher well-being, creativity, job satisfaction, and commitment, among other positive leadership outcomes.

At the same time, it is important to note that these relationships may be contingent on certain factors such as the cultural environment (Jackson, Meyer, and Wang 2013; Koh, Lee, and Joshi 2019). Nonetheless, organisations are likely to yield the best results across a range of outcomes when HRD professionals seek to encourage and develop transformational leadership in their leaders. Thus, our review encourages the continued use of evidence-led practices in leadership development initiatives.

Limitations

Although our paper reviewed positive and active forms of leadership behaviours, it did not cover other passive (e.g. laissez-faire ‘non-leadership’ which reflects the avoidance of acting; Bass 1999) and destructive forms of leadership (i.e. ‘styles of leadership comprised of behaviours … that harm followers and/or organisations’ [Mackey et al. 2021, 705]). Overall, the meta-analytic evidence suggests that negative leadership styles can have detrimental effects on various leadership outcomes. For instance, abusive supervision is associated with higher levels of stress and burnout among followers (Harms et al. 2017) and authoritarian leadership is negatively related to innovation (Lee et al. 2020). Likewise, Judge and Piccolo (2004) found that laissez-faire leadership was negatively related to leader effectiveness. This result is further corroborated with DeRue’s et al. (2011) finding that laissez-faire leadership behaviours were the strongest predictor of leader (in)effectiveness, explaining 11.6% of the variance in leader (in)effectiveness. Taken together, extant research reminds us that negative and destructive forms of leadership may also be important and unique contributors in predicting various outcomes. Therefore, a two-pronged approach in the practice of leadership development – aimed at identifying and discouraging negative leadership behaviours while also encouraging and developing positive leadership behaviours – may be best.

Practical implications

Our review suggests that transformational leadership is an effective model to embed within leadership development initiatives. Initiatives based on this model can teach leaders positive, effective leadership behaviours as well as provide opportunities to practice and improve on these behaviours. The main benefit of focusing on transformational leadership is that it consists of four components (i.e. idealised influence, intellectual stimulation, individual consideration, and inspirational motivation). This is not to oversimplify leadership but concentrating efforts on these four highly correlated behaviours can be practically advantageous, as initiatives designed and delivered around these behaviours are likely to be more digestible than creating initiatives for multiple leadership models and their respective behaviours. As previously discussed, the constructs proposed by new leadership models may tap into the same construct as transformational leadership, offering only incremental benefits (if any) for training leaders. An additional practical advantage of focusing on transformational leadership is the potential for improving efficiency in assessing the transfer of knowledge in the workplace. Rather than measuring and observing multiple behaviours, HRD professionals can narrow their focus, observing and measuring only the four transformational leadership behaviours. In summary, by focusing on one central leadership model – transformational leadership – organisations and HRD professionals can maximise their limited resources.

Based on the meta-analytic research reviewed, we outline the main take-away points and recommendations for HRD professionals in Table 4.

Table 4. Main take-away points and recommendations for HRD professionals.

Practical points	Summary
Point #1	Current evidence suggests that new leadership models (i.e. authentic leadership, ethical leadership, and servant leadership) may overlap with transformational leadership such that they may be tapping into the same thing.
Point #2	The evidence also suggests that the unique contribution from new leadership models in predicting various outcomes of leadership is relatively small compared to that of transformational leadership. Although some leadership models may substantially add to the prediction of certain outcomes, it is unclear whether these unique contributions will translate into noticeable changes.
Point #3	A plethora of empirical evidence suggests that transformational leadership is positively and strongly related to various outcomes of leadership (see Table 2).
Recommendations	Summary
Recommendation #1	Based on practical point 1 and 2, we advise HRD professionals to focus leadership development initiatives around one leadership model: transformational leadership.
Recommendation #2	Based on practical point 3, leadership development initiatives and activities may be designed around the four behaviours of transformational leadership – idealised influence, inspirational motivation, intellectual stimulation, and individual consideration – to enhance various individual, team, and organisational outcomes.

Conclusion

In this paper, we sought to distil the transformational leadership research into a primer of evidence-led practices for HRD professionals and organisations to use in their leadership development initiatives. Our review of meta-analyses in this area found that transformational leadership had medium to large effect sizes on a range of outcomes, demonstrating its consistent and strong links with individual, team, and organisational outcomes. Thus, our primer suggests the importance of grounding leadership development initiatives in transformational leadership.

Acknowledgement

We would like to thank Jennifer Krahn, Catie Phares, Glenda Reynolds, and Natalie Valle for feedback on earlier versions of this paper.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Canadian Centre for Advanced Leadership in Business.