Half of working Americans (49 percent) have suffered or witnessed workplace bullying — including verbal abuse, job sabotage, abuse of authority or destruction of workplace relationships, according to a new Workplace Bullying Institute/Zogby Interactive survey.

The WBI survey found that 37 percent of the U.S. workforce, an estimated 54 million employees, have been bullied now or sometime during their worklife. Yet, despite this prevalence, 45 percent of respondents said they have never seen or experienced bullying at work.

"It's clearly a 'silent epidemic,'" says Dr. Gary Namie, Director of the Workplace Bullying Institute in Bellingham, Wash.

Stress from prolonged exposure to bullying — 33 percent suffer for more than one year — adversely affects psychological or physical health of 45 percent of targets.

Regarding gender, the survey reveals that when bullies are women, they choose other women as their prey in 71 percent of cases. Bullying, or status-blind harassment, is four times more prevalent than illegal, civil rights, status-based harassment. Same-gender harassment defines the two most frequent categories of bullying. "It was legal when we started the movement in '98 and it still is today," said Namie.

According to the survey, bullying can be costly to employers. Since 40 percent of bullied respondents left their jobs, it is estimated that the skills of more than 21 million workers are lost to employers due to bullying. Yet, when employers are notified, in the majority (62 percent) of cases, they do nothing or make matters worse. Employer indifference may be based on these findings: most bullies are bosses (72 percent); bullies enjoy support from executive sponsors, peers and human resources; most targets are non-supervisory workers (55 percent); and in 80 percent of cases, it is legal.

The nationwide interactive survey was conducted August 10-13, 2007, and included 7,740 respondents. The measure of error is +/- 1.1 percentage points. This is the largest, national, representative study of the phenomenon in the U.S. to date.

Results can be found online at bullyinginstitute.org.