Defying conventional wisdom: A meta-analytical examination of the differences between demographic and job-related diversity relationships with performance

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Abstract

Conventional wisdom in the diversity literature holds that job-related dimensions of diversity are the domain of positive performance, whereas demographic dimensions of diversity are the domain of negative performance effects. In a meta-analysis (N = 146 studies, 612 effect sizes), we show that this conclusion may be based on rater biases; it does not apply to studies involving more objective assessments of performance, assessments that cannot be influenced by knowledge of a team’s composition. We also show that the influence of job-related diversity is moderated by task complexity and that job-related diversity is more positively related to innovative performance than to in-role performance. We discuss how these results invite a reconsideration of the role of the job-related/demographic diversity distinction and provide suggestions on how to further advance our understanding of diversity’s effects.

Highlights

► We meta-analytically contrast demographic and job-related diversity. ► We show that rater biases impact the diversity–performance relationship. ► We find that task complexity moderates the influence of job-related diversity.

Introduction

As societies become increasingly diverse and organizations increasingly rely on cross-functional teams to address complex and challenging issues, the question of how work group diversity affects work group performance is of greater relevance to research and practice than ever before (Plaut, 2010). With the growth of research on the diversity–performance relationship, it has become more and more clear that there is no straightforward answer to this question. Indeed, it has become a truism that diversity is a double-edged sword (Milliken & Martins, 1996). Nearly all dimensions of diversity that have received research attention have yielded positive, negative, and nonsignificant relationships with performance (Jackson et al., 2003, van Knippenberg and Schippers, 2007, Williams and O’Reilly, 1998). The state of the science thus suggests that in order to advance our understanding of the relationship between diversity and performance, we should look for moderators of the diversity–performance relationship (van Knippenberg, De Dreu, & Homan, 2004).

Meta-analysis of research findings is particularly suited to address this issue, because meta-analysis allows for cross-study comparisons that can identify moderator variables not captured by primary research. Although we are not the first researchers to conduct a meta-analysis of the diversity–performance relationship, our analysis includes more than two (Bell, Villado, Lukasik, Belau, & Briggs, 2011) to five (e.g., Joshi & Roh, 2009) times as many effect sizes as earlier analyses, which is an important advantage in the search for moderators. Indeed, our more elaborate moderator analysis overturns several of the conclusions from those earlier analyses, as well as conventional wisdom in the field.

In attempts to make sense of the disparate findings involving diversity and performance, the longest-standing proposition is that diversity’s effects are somehow contingent on the dimension of diversity that is assessed (e.g., Jehn, Northcraft, & Neale, 1999). According to this viewpoint, demographic dimensions of diversity (e.g., age, gender, ethnicity) are primarily linked to the negative performance effects of diversity, whereas job-related dimensions of diversity (e.g., functional background, tenure) are primarily linked to its positive performance effects. Recent analyses seem to support this notion (Horwitz and Horwitz, 2007, Joshi and Roh, 2009). As a result, the moderating role of diversity “cluster” (demographic versus job-related) has come to seem like one of the few things that we know about diversity (Mannix & Neale, 2005).

We argue against this conventional wisdom. We propose that it reflects diversity-related biases in the subjective (e.g., team member, team leader) ratings of performance used by many researchers, and that it would be untrue if group performance were measured in more objective ways (e.g., financial performance or number of ideas generated).

As part of our focus on demographic versus job-related diversity, we have also conducted a more comprehensive analysis of the moderating role of task complexity in the diversity–performance relationship. In their meta-analysis, Bowers, Pharmer, and Salas (2000) showed that diversity was more helpful for performance on more complex tasks, but this finding was not supported in a more recent meta-analytical test (Horwitz & Horwitz, 2007). We propose that this discrepancy arose because earlier work did not consider the possibility that task complexity only moderates the relationship between performance and job-related diversity (diversity in attributes that are related to the knowledge and expertise that are required to solve highly complex problems). Moreover, we extend and qualify earlier analyses (e.g., Bell et al., 2011, Hülsheger et al., 2009) of the distinction between in-role and innovative performance by arguing that diversity overall (not just job-related diversity) is more positively related to innovativeness and creativity than it is to performance that is part of the team members’ regular work.

Section snippets

The double-edged sword of diversity

Diversity is a group characteristic that reflects the degree to which there are objective or subjective differences among members (van Knippenberg & Schippers, 2007). Diversity may concern differences in demographic characteristics, such as age, gender, or ethnicity; job-related characteristics, such as functional background or organizational tenure; deeper psychological characteristics, such as personality, attitudes, and values; or other attributes. Although diversity can (in principle)

Diversity clusters revisited

Several recent meta-analyses provide support for this proposition (Horwitz and Horwitz, 2007, Joshi and Roh, 2009; cf. Hülsheger et al., 2009). At first blush, this seems to prove that the conventional wisdom about diversity is correct. But a closer consideration of the issue suggests to us that this conclusion is unjustified. First, several authors have noted that demographic diversity is sometimes associated with valuable difference in task-related information (Cox, 1993, Ely and Thomas, 2001

Sample of studies

Several sources were used to identify relevant studies. First, ISI Web of Knowledge, PsychInfo, ABI/INFORM, Educational Resources Information Center (ERIC), and ProQuest Digital Dissertations were used in a computerized search. Specific keywords used to search for relevant studies in these electronic databases were team or group heterogeneity or composition or diversity (and faultline/faultlines) in combination with performance, innovation, or creativity (as potential indicators of innovative

Characteristics of the studies

Table 1 presents a summary of the characteristics of the studies included. The 146 studies produced a total of 612 effect sizes. There were 1–28 (Giambatista, 1999) effect sizes per study. The number of groups within the studies per study ranged from 12 (Daily et al., 1996) to 4845 (Richard & Shelor, 2002), with a median of 59 work groups. Average group size ranged from 3 to 22.8 (Wegge, Roth, Neubach, Schmidt, & Kanfer, 2008) per study, with a median of 5.4 members.

Outliers

Eleven effect sizes were

Discussion

At first blush, diversity is a field of research with highly inconsistent findings. It is thus the kind of field where meta-analysis is an important tool for determining what we can, and cannot, conclude on the basis of the available evidence. One of the key issues in diversity research is whether the kind of diversity – demographic versus job-related – moderates its performance effects. Recent meta-analyses appeared to support a conclusion that has long been endorsed by many researchers,

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    Parts of this paper were presented at the Annual Meeting of the Academy of Management, Chicago, IL, August 2009.

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