Federal employees filed slightly fewer discrimination complaints against their agencies in 2011. However, employees who pursue their challenges through additional steps are waiting nearly a year for hearing decisions and more than a year for appeal decisions, according to data released Monday.

The Equal Employment Opportunity Commission’s annual report on its federal sector case processing showed that about 15,800 individuals filed a total of about 17,000 complaints in fiscal 2011 — a drop of about 4 percent from 2010.

The most common basis for a complaint was retaliation, followed by age discrimination and race discrimination. The most frequently cited action was non-sexual harassment, followed by non-selection for promotion and changes in conditions of employment.

The bias complaint process works differently within the federal government than it does in the private sector. Federal employee complaints are first investigated by their own employing agency. Employees unhappy with the outcome can move on to a hearing before an EEOC hearing officer called an administrative judge, and from there can appeal to the EEOC central office.

EEOC said that about three-fourths of agency investigations were finished within the 180-day time limit. Especially quick performance by the U.S. Postal Service pulled up the government-wide average.

However, higher numbers of employees continued their cases past the agency level and found the waits longer.

Specifically, employee requests for hearings by administrative judges rose by about 5  percent to about 8,100, and the average processing time for those challenges rose by 4 percent, to 345 days. The number of cases awaiting hearings was up 12 percent and has grown by nearly half since fiscal 2007, topping 8,000.

Meanwhile, the number of appeals to the commission rose by 14 percent to almost 5,200, and processing time there rose by 30 percent to 378 days. About 4,300 cases are pending there, up by 18 percent from 2010 and up by about a quarter since 2007.

Agencies with the highest rates of complaints included the Government Printing Office, the Housing and Urban Development and Education departments and the Defense Department’s Washington headquarters.

EEOC said that 53 percent of employees who used alternative dispute resolution methods did not go on to file formal complaints.