At a Congressional hearing earlier this month, Del. Eleanor Holmes Norton (D-D.C.) appeared frustrated. A new report on legislative branch agencies’ diversity in senior positions proved disappointing, and a Government Accountability Office official couldn’t answer many of her questions.

Why, she wanted to know, did the GAO wait so long to address the fact that overall, black employees at the agency get lower performance ratings than their white peers? And knowing this, why did the agency move ahead with implementing a new pay system partly based on those same ratings?

Ronald Stroman, managing director of the Office of Opportunity and Inclusiveness, couldn’t answer. The ultimate decision, he said, simply was not his call.

“I tell you who is going to have to make the call. The Congress is going to have to make the call,” Norton said. “This is an outrage.”

Every year since 2002, Stroman’s office has found a disparity between the annual performance reviews, or appraisal ratings, of black and white GAO analysts. Those reviews are integral to moving up within the agency — they determine raises, annual bonuses and promotions. Get a lower rating than your peers, and you risk getting stuck on one rung of the promotional ladder.

But while data have shown that black employees get lower ratings than their colleagues, it’s hard to pin down the reason: Are some black analysts less qualified than their white counterparts? Is the system intrinsically biased? Or is it outright discrimination?

To find out, the GAO has hired the Ivy Planning Group, a Maryland-based consulting company. It’s the agency’s solution to a problem that has gotten more attention since a controversial restructuring of the pay system. In an annual progress report released Thursday, the GAO was mostly positive about its own performance, finances and internal workings. The ratings system was one of the rare exceptions.

“When I looked at some of the recent trends for performance ratings for African-Americans, I was concerned,” Comptroller General David Walker, who heads the agency, said in an interview. “I wanted to understand what was behind those trends, and there may very well be an explanation, but I didn’t want to assume one way or the other.”

This doesn’t mean black employees aren’t promoted. A recent study found that black employees make up more than 10 percent of the agency’s top positions. And the difference in ratings, on first glance, seems small. On a scale of 0 to 5, with 5 representing the highest rating, black employees’ scores on the whole were less than 0.3 points lower than other racial groups. But it’s statistically significant, and with average scores mostly hovering between 2 and 2.5, a few tenths of a point make a difference. Enough of a difference that the GAO is spending $500,000 to get it all explained.

“Just because there’s a difference doesn’t mean there’s discrimination,” Walker said. “By definition there’s going to be a difference. The question is why there’s a difference.”

The Ivy Planning Group will tackle the question in a three-step process, according to documents from an October meeting. First, it will analyze the ratings data on its own to determine if the difference is “significant.” Then, it will compare the skills of incoming black and white employees, following the path of ratings issued in the years after they arrive. Finally, it will study the system itself and come up with recommendations. Sprinkled in between will be focus groups and meetings with executives. It’s all expected to be done by the end of fiscal 2008.

“I’m hopeful,” said Mary Crenshaw, a black senior analyst who is acting as the GAO union’s liaison for the study. “I’m just hopeful that this study will really show that there are systematic types of things that really put African-Americans at a disadvantage.”

But Norton’s concern that the study is too late is a widespread one. GAO knew of the disparity back in 2004, when Blacks in Government alerted the agency to the consequences. The group asked that Walker delay his plan to restructure the agency’s pay system, which would split certain analysts into two different “pay bands” — one more senior than the other — partially based on the performance ratings.

But in the end, Walker went ahead with his plan. Some claimed it negatively affected black employees, many of whom had ratings that weren’t high enough for acceptance into the more senior band. Of course, the system also sparked controversy for other reasons, including its cap on salaries, and in the end it incited employees to create the agency’s first union.

“You can’t put an agency on hold with regard to all the reforms based on one issue,” Walker said. “You have a trade-off. Do you allow one ineffective and unsustainable situation to continue until you do a study … or do you go ahead and do what you think is in the best interest of the agency?”

Walker said that at the time, he was confident new hiring practices would eliminate any significant disparity in new employees. The disparity, he said, had existed long before he entered office in 1998. Walker said he believed that by revamping the agency’s hiring practices, it would eventually disappear. He expected to see it in older employees for a while, he said, because in the past GAO wasn’t “consistent” in how it hired many of those employees — basically, black employees may have come in with less experience and qualifications than their white counterparts.

But when disparity began to show up again in the entry-level positions, he thought it was time to take action. And so far, the Ivy Planning Group has found that the new review system may be related to the difference in ratings — when officials removed some of the criteria used to rate employees, the disparity increased.

“Could we have done it a year earlier? Maybe,” Walker said. “What I think people need to keep in mind is it’s unprecedented what we’re doing.”

Shirley Jones, president of the GAO’s Blacks in Government, said she believes Walker was acting in good faith when he went forward with the restructuring.

“I understand why they didn’t halt the process,” said Jones, a GAO assistant general counsel. “I truly believe that Mr. Walker thought that the situation was going to be rectified by changes he already implemented and I also believe that in some respect he thought he couldn’t necessarily fix problems from the past.”

But the effect of the restructuring was evident, she said: “It’s definitely clear that African-Americans were disproportionately affected.”

Some question whether it’s too late — the damage, they say, is already done. Crenshaw said she hopes the company will recommend that changes be made to the band restructuring, though that seems unlikely.

“I would like for whatever they do to affect things retroactively. I know that may sound kind of grand, but I think that is what has to be done,” she said. “You’ve got all of these people that were wounded, and there needs to be something that addresses that.”