President Barack Obama has been criticized for a lack of diversity in his cabinet compared to his predecessor - charges he also faced when he was president of the Harvard Law Review and only 25% of editors chosen by him were women. His Supreme Court Justices, Sonia Sotomayor and Elena Kagan, were women but their selection meant that all 9 Supreme Court Justices have been chosen from a 230 mile section of the United States - two Ivy League Schools, Harvard and Yale, making decisions for all Americans. Critics again claimed a lack of diversity.

While not blazing any trails, the Obama administration has made the Supreme Court less homogenized than in the past - you just have to use statistical methods borrowed from ecology,  the Simpson's Diversity Index and Shannon's Diversity Index, to frame it positively. A paper in the Journal of Empirical Legal Studies examined seven categories of diversity for every Supreme Court justice since the Court first convened in 1790 with Justice John Jay, including ethnic/racial origin, religion, professional background, childhood economic background, geographic background, education, and political affiliation. 

Gender was not included in the study because until President Ronald Reagan tore down the gender barrier there were no women, so it would score almost constantly zero if gender were factored in.

The model showed that the current Supreme Court is slightly more diverse than it has been historically, in professional background, childhood economic background and racial origin, but there is a worrisome trend due to lack of geographic background differences and religious affiliation, with Protestantism and other major religious groups showing less representation today. As is well known, the Court completely lacks in educational diversity with every justice having attended either Harvard or Yale Law Schools.

"The lack of educational diversity is worrisome. Diversity is good in a small decision-making body. Studies have shown that it sparks creativity and improves decision-making," Ben Barton, the study's co-author and professor of law at the University of Tennessee-Knoxville (UTK), said in a statement.

One of the goals of the study was to apply statistical techniques that have been used reliably by ecologists to study biodiversity but have never before been used in the study of law. The two statistical indices used – the Simpson's Diversity Index and Shannon's Diversity Index – are common and high-regarded measures used in ecology since the 1940s.

"These indices take into account both the number of categories represented – such as species or religions – and the evenness with which they are represented. Just as a forest that is 90 percent maple with three other species at low abundance is generally considered less diverse than one in which all four species are at similar abundance, a human group must move beyond 'token' representation before it can be considered truly diverse," said co-author Emily Moran, postdoctoral researcher at the Swiss Federal Institute of Technology in Zurich, Switzerland. 

Citation: Benjamin H. Barton and Emily Moran, 'Measuring Diversity on the Supreme Court with Biodiversity Statistics', Journal of Empirical Legal Studies Volume 10, Issue 1, pages 1–34, March 2013 DOI: 10.1111/jels.12000 (open access)