A year as a U.S. Supreme Court law clerk is a priceless ticket to the upper echelons of the legal profession. Former clerks have their pick of top-tier job offers and can command $350,000 hiring bonuses at law firms.

Four current justices were formerly clerks at the court—a record number—and three U.S. senators are former clerks. The general counsels of both Apple and Facebook once clerked at the high court. For aspiring appellate litigators and academics, a Supreme Court clerkship opens the creakiest doors.

But amid the luster of being a law clerk, there's an uncomfortable reality: It is an elite club still dominated by white men. While some variables are outside the court's control, few justices seem to be going out of their way to boost diversity.

Research conducted by The National Law Journal found that since 2005—when the Roberts court began—85 percent of all law clerks have been white. Only 20 of the 487 clerks hired by justices were African-American, and nine were Hispanic. Twice as many men as women gain entry, even though as of last year, more than half of all law students are female.

The numbers show near-glacial progress since 1998, when USA Today and this reporter undertook the first-ever demographic study of Supreme Court clerks, revealing that fewer than 1.8 percent of the clerks hired by the then-members of the court were African-American (now it is 4 percent,) and 1 percent were Hispanic (now the figure hovers at roughly 1.5 percent). The percentage of clerks who are of Asian descent has doubled from 4.5 percent then to nearly 9 percent since 2005. Then, women comprised one-fourth of the clerks; now they make up roughly a third.

Of the 36 clerks hired by sitting justices this term, one is African-American, two are Hispanic, and three are Asian-Americans, based on the NLJ research.

The ranks of Supreme Court clerks are less diverse and more male than law firm associates, while the stakes for society are certainly higher. Clerks play a crucial role in helping justices pick which cases to grant, and in writing opinions. In both of those roles, the lack of diversity among clerks means the court's handling of race and immigration cases, among others, continues to be shaped by players who have little personal experience to inform the discussion.