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by Julia DiPrete | December 09, 2022


If you’re an avid reader of our Vault rankings and profiles, you’ve certainly come across references to the Mansfield Certification. Firms that have achieved this certification will usually list it among their “Notable Awards,” and for good reason: Mansfield Certification, while relatively new, has become an important and powerful indicator of a firm’s commitment to diversity and inclusion through commitment to the “Mansfield Rule.” In this blog post, we provide an overview of what the Mansfield Rule is, how a firm earns certification, and what the Rule hopes to achieve.

Diversity Lab: The Origin of the Mansfield Rule

Diversity Lab is the brainchild of Caren Ulrich Stacy, formerly head of talent and diversity for many of the world’s top law firms. Ms. Stacy founded Diversity Lab in 2013 as an “ideas incubator” for increasing diversity, equity, and inclusion in the workplace (in the legal industry and beyond) through the use of data, science, and technology.

The Lab uses models typically associated with the tech industry to find innovative solutions; in particular, the Lab has run a series of “hackathons” partnered with top law schools that have led to some of its most successful initiatives.

Notably, in 2016, the Lab collaborated with Stanford Law School and Bloomberg News to host the first ever “Women in Law Hackathon” described on the Diversity Lab website as “a Shark Tank-style pitch competition aimed at generating ideas to boost the retention and advancement of women in law firms.” This Women in Law Hackathon was the genesis for what would become known as the Mansfield Rule.

What is the Mansfield Rule?

Football fans may be familiar with the Rooney Rule, which is an NFL policy requiring any team with a head coach vacancy to interview at least one or more diverse candidates for the role. The Mansfield Rule–named after Arabelle Mansfield, the first woman to become an attorney in the US in 1869–is similarly designed to boost the representation of diverse individuals in leadership by broadening the pool of candidates considered for these opportunities.

The foundation of the Mansfield Rule is behavioral science (also known as behavioral economics), which “studies when and why individuals engage in specific behaviors by experimentally examining the impact of factors such as conscious thoughts, motivation, social influences, contextual effects, and habits.” In other words, behavioral science looks at which factors influence humans to do the things we do.

A key pillar of the Mansfield Rule, and a striking demonstration of behavioral bias, is the 30% (or the 30-50%) consideration requirement. A Harvard Business Review study looked at the likelihood of a woman being hired for a role based on the gender composition of the candidate pool. This study found that statistically, a woman has almost no chance of being hired if she is the only woman in a candidate pool; adding a second woman to the pool increased the chances of a woman being hired by almost 80% (these results were the same in pool sizes from three up to 11 people, and also the same when race was studied instead of gender).

Let that sink in. Increasing the number of diverse candidates in a pool from one person to two people increases the likelihood of a diverse hire by almost 80%. But why?

The answer is unconscious bias. Without getting too far into the weeds, behavioral science demonstrates that one woman in an otherwise male candidate pool highlights her differences, and difference makes people nervous (in the same way that familiarity makes people feel safe). We emphasize the “unconscious” aspect of this bias because these results hold true even within organizations purportedly committed to diversity, equity and inclusion.

By requiring 30% consideration of diverse candidates in a hiring pool, the Mansfield Rule aims to disrupt this unconscious bias–with striking results.

What is Mansfield Certification and How Does a Law Firm Achieve It?

Mansfield Certification has undergone multiple iterations since the launch of Mansfield Rule 1.0 in 2017. In this pilot version, the main requirement was to consider at least 30% women lawyers and underrepresented racial and ethnic lawyers for leadership roles. Each iteration has expanded the program, to include LGBTQ+ lawyers and lawyers with disabilities as well as increase transparency in hiring.

Certification is a year-long process during which firms must:

  • Share lessons with each other through monthly knowledge-sharing forums;
  • Create and publish job descriptions for leadership roles; and
  • Continue to meet routine check-in, data-collection, and reporting milestones.

Diversity Lab collaborates with participating law firms throughout the certification year, offering support and resources as well as overseeing firm efforts.

In addition, firms can also achieve Mansfield Plus Certification, which indicates that, in addition to meeting or exceeding the baseline requirements, the firm has met the goal of at least 30% diverse lawyer representation in a notable number of its current leadership roles.

Mansfield Certification is Growing, and it’s Working 

In the five years since its inception, Mansfield Certification has expanded dramatically from its initial participating group of 35 law firms; in 2022, there are 270+ U.S. and Canadian law firms, 15+ UK law firms, and 75+ legal departments participating in the 5.0 certification process.

Results have been striking. Full results would be far too copious to include; to summarize, according to a recent Bloomberg Law report, “the 30+ early adopter law firms—those that have achieved certification year-over-year since the rule’s launch in 2017—have made progress above and beyond the typical rate of change pre-Mansfield. In several instances, Mansfield firms have significantly increased the racial and ethnic diversity of their leadership and outpaced non-Mansfield firms’ progress.”

We strongly encourage you to take a deeper dive into the work being done by Diversity Lab, both on the Mansfield front and beyond. For a full list of participating 5.0 firms and more details about their accomplishments, read a Diversity Lab press release.