The study is here, hat tip to the Monkey Cage, a great site. I should say historically biased, since the study goes back to 1960.
The abstract:
This paper uses two new datasets to investigate the reliance by political actors on the external vetting of judicial candidates, in particular vetting conducted by the nation’s largest legal organization, the American Bar Association (ABA). First, I demonstrate that poorly rated lower-court nominees are signicantly more likely to have their nominations fail before the Senate. However, I also show that minority and female nominees are more likely than whites and males to receive these lower ratings, even after controlling for education, experience, and partisanship via matching. Furthermore, by presenting results showing that ABA ratings are unrelated to judges’ ultimate reversal rates, I show that these scores are a poor predictor of how nominees perform once confimed. The findings in this paper complicate the ABA’s influential role in judicial nominations, both in terms of its utility in predicting judicial performance and also in terms of possible implicit biases against minority candidates, and suggest that political actors rely on these ratings perhaps for reasons unrelated to the courts.
An excerpt:
Despite attempts by Presidents and by advocacy groups, federal courts in the United States are still unreflective of the U.S. population. Of the 874 federal judges in service as of 2008, only 24% were women, 10% were African American, and 7% were Hispanic …. Fewer than 1% were Asian American and, even today, there are no federal judges who self-identify as Native American — surprising given the courts’ involvement in interpreting federal Indian laws.