The issue of sexual harassment in the workplace was seared into the national consciousness when, in 1991, Anita Hill accused Clarence Thomas of making harassing sexual statements at his confirmation hearings to be a US Supreme Court justice.

Since then, businesses have undertaken countless hours of sexual harassment seminars, employers have heeded legislation that makes them liable for punitive damages in these kinds of cases, and several high-profile class action lawsuits – particularly in the 1990s – have ended in the awarding of big damages to victims of harassment.

Yet even with all this, workplaces have seen sexual harassment claims go down just slightly in the past decade.

Now, some 20 years after the Thomas hearings, sexual misconduct allegations against GOP presidential hopeful Herman Cain are drawing fresh attention to the issue of sexual harassment.

In particular, the controversy surrounding Mr. Cain has put a spotlight on secret settlements – legal agreements with confidentiality clauses that prohibit accusing parties from disclosing details about the alleged misconduct, in return for money or other benefits.

The National Restaurant Association, which Cain headed in the late 1990s, entered into secret settlements with two women who accused the businessman of unwanted sexual advances. The NRA reportedly paid the women $35,000 and $45,000.

Such settlements are gaining popularity, say workplace discrimination experts. With these secret agreements, employers can avert costly legal fees, and as important, damaging publicity. But many see worrisome consequences.

The use of confidential settlements "started in the '90s, and it's really taken off since," says Julie Berebitsky, a professor of history and women's studies at the University of the South in Sewanee, Tenn., and author of the forthcoming book "Sex and the Office: A History of Gender, Power, and Desire." She adds, "Moving forward, I think that's where we're headed."

As of press time, four women had made sexual harassment accusations against Cain, a front-runner in the GOP presidential field. Of the NRA cases, one woman has revealed her identity – Karen Kraushaar, now a spokeswoman for the Treasury Department. She had not disclosed details of the case as of Nov. 9, but she did allege that Cain made a "series of inappropriate behaviors and unwanted advances."

The other accuser to go public, Sharon Bialek, claimed that Cain reached up her skirt, saying when she protested, "You want a job, don't you?"

Cain emphatically denies all the allegations. In a CBS News poll conducted from Nov. 6 to 10, he holds the top spot among GOP presidential candidates. But the poll also indicates that he has lost some support, particularly among women and conservatives.

The landmark Civil Rights Act of 1964 made race-, religion-, and sex-based discrimination illegal. The term "sexual harassment" was coined by feminists in 1975, and soon after, courts began holding that it was prohibited in workplaces under Title VII of the act.

The Equal Employment Opportunity Commission, which tracks workplace discrimination, defines sexual harassment as "unwelcome sexual advances, requests for sexual favors, and other verbal or physical harassment of a sexual nature." The EEOC adds, "Harassment does not have to be of a sexual nature, however, and can include offensive remarks about a person's sex."

Sexual harassment claims climbed through the 1990s, peaking at 15,889 in 1997, according to the EEOC. (Reliable figures are not available for years prior to 1990.) Claims began dropping off in the 2000s, falling to 11,717 in 2010, which yielded some $48.4 million in monetary benefits for charging parties. That dollar figure comes from settlements that involved the EEOC but not from damages obtained through litigation.

The drop in claims may reflect better workplace training on sexual harassment – or it may simply reflect a challenging economic climate that makes employees more fearful of reporting sexual harassment for fear of jeopardizing their jobs or career advancement, says David Yamada, a Suffolk University law professor and president of the New Workplace Institute in Boston.

It's also possible that the number of confidential settlements has meant fewer claims filed with the EEOC.

To be sure, the claims figures don't capture the full scope of sexual harassment, says Christine Nazer, a spokeswoman for the EEOC.

"We believe these numbers of sexual harassment are the tip of the iceberg," Ms. Nazer says. "There may be thousands or millions of incidents that go unreported."

Some estimates suggest that only 5 to 15 percent of those who feel they experienced sexual harassment file complaints.

The handling of those claims that are filed tells an interesting story. Of the 11,717 claims last year, some 6,393 were found to have "no reasonable cause." That is, more than 50 percent of the claims were thrown out. This points to a broad misunderstanding of what actually constitutes sexual harassment, says Curt Levey, executive director of the Committee for Justice in Washington and an attorney specializing in civil rights law.

"The public definition has become very different than the legal definition," he says. "It's not behavior I would approve of, but there's a big difference between crude behavior and actual sexual harassment.... Title VII and other sexual harassment laws were intended to protect people from adverse conditions in the workplace, not from every unwanted sexual advance."

Also, in some cases, as with Cain and former International Monetary Fund chief Dominique Strauss-Kahn, it is difficult to establish the veracity of accusers. Many incidents become a tangled web of "he said, she said" allegations.

According to Mr. Levey, confidential settlements can be an efficient way for an employer to settle a claim, whether or not it constituted sexual harassment.

The use of in-house arbitration and confidential settlements became standard practice in the early '90s, when President George H.W. Bush signed into law the Civil Rights Act of 1991. This allowed sexual harassment plaintiffs to receive money for emotional distress and punitive damages, says Professor Berebitsky.

"Companies could take a bath if found guilty," she says. "Employers said, 'We have got to limit liability.' That gave employers an impetus to get on the arbitration train."

Today, many employers require their workers to sign arbitration agreements that say, "in case of any claim of discrimination, you won't go to the courts but agree to enter into binding arbitration," says Berebitsky.

That tactic shields harassers and employers from accountability, says Professor Yamada.

"I am very concerned about confidentiality clauses being standard practice," he says. "If harassers are not disciplined or discharged as part of the settlement, it's quite possible that they will mistreat others in the same way.... Overall, confidentiality clauses allow bad employers to cover multitudes of sins."

Levey disagrees. "The efficient functioning of the justice system depends on the large majority of complaints – sexual harassment and otherwise – being settled. If confidentiality provisions were barred, there would be less incentive to settle and thus more litigation," he writes in an e-mail. "Moreover, it would hardly be justice to hold accused employers and harassers publicly accountable when the evidence of guilt is scant, as is often the case for settled complaints."

Michael R. Masinter, a law professor at Nova Southeastern University in Fort Lauderdale, Fla., sees the issue of public accountability differently.

"[T]he combination of arbitration agreements ... and confidential settlements can conceal the scope of a problem that, were it known, would inspire public outrage," he writes in an e-mail. It leaves "the false impression that sexual harassment is a thing of the past when it is still very much a part of the contemporary workplace."