Law firms that were early adopters of a pilot programme to boost the diversity of their leadership teams based on the NFL’s Rooney Rule have seen improvements at more than 30 times the rate seen at non-adopting firms.

The Diversity Lab’s so-called Mansfield Rule – whose first iteration back in 2017 was signed up to by 41 firms including Bryan Cave Leighton Paisner, Clifford Chance, Jenner & Block, Latham & Watkins and McDermott Will & Emery – is designed to grow the racial and ethnic diversity of those firm’s management committees so that at least 30% of candidates are from underrepresented groups.

An analysis of the data of firms that have completed the first two Mansfield Rule certification cycles show that growth in underrepresented racial and ethnic lawyers outpaced non-Mansfield Rule firms by more than 30 times between 2017 and 2019. 

Lisa Kirby, Diversity Lab’s chief business intelligence and knowledge sharing officer, said: “These firms have operationalised the Mansfield Rule’s principles so that their achievements are part of a movement rather than a moment. As a result, these gains are not vulnerable to the shifting winds of the marketplace.”

Mansfield Rule firms are also improving racial diversity of partnerships at a faster clip than they were pre-Mansfield. By 2019, Mansfield firms saw the percentage of their partners considered racially diverse increase to 10.5% compared to 9.1% for non-Mansfield firms. Diversity Lab said that divergence is significant based on broader data from 2007 to 2019 when large firms only increased the racial diversity of their partnerships by 0.2% on average every year.

Diversity Lab said women lawyers from early-adopter firms are also progressing into leadership roles at a higher rate than they were pre-Mansfield, though it added that non-Mansfield firms are also making progress on gender diversity.

Since the Mansfield Rule was first introduced, almost 120 firms have now signed up, with later iterations of the rule also including goals to boost the number of LGBTQ+ lawyers and lawyers with disabilities. Diversity Lab is also planning to introduce similar pilot programmes for mid-size law firms, corporate legal departments and UK firms. 

Last year, five law firms committed to spend more than $5m exploring how to improve diversity and inclusivity over a five-year period as part of the Move the Needle Fund, which is run by Diversity Lab.