There is broad agreement that the restaurant industry is rife with sexual harassment.

More than 70% of female restaurant employees have been sexually harassed, one recent survey found, and half experience sexual harassment on a weekly basis, according to another. Harassment complaints come to the Equal Employment Opportunity Commission from restaurant industry workers more often than from any other sector.

Now a new two-part scientific study looks to confirm why.

Dependence on tipped wages, along with job requirements to appear friendly and pleasant — in other words "service with a smile" — jointly create a culture of sexual harassment, according to a team of researchers at the University of Notre Dame, Penn State University and the Emlyon Business School in France, who say their study is the first to provide an empirical link between tipping and sexual harassment.

"Much of the research and media attention has focused on why organizational insiders, or other employees engage in sexual harassment. It really didn't address why service employees were likely to face sexual harassment from organizational outsiders, like customers," said Timothy Kundro, a professor at Notre Dame's Mendoza College of Business. "We wanted to uncover what factors could be driving this given its prevalence."

The research, recently published in the Journal of Applied Psychology, had two parts.

First, Kundro and his co-authors surveyed 92 full-time service employees about their income, whether they were required to appear positive at work and how frequently they experienced sexual harassment.

Then they recruited more than 200 men to participate in an online experiment where the men played the role of the customer as researchers adjusted variables such as the waitress' facial expression and whether the waitress was dependent on tips.

The results, they said, confirm that dependency on tips and a requirement to appear emotionally pleasant on the job work together to increase an employee's risk of being sexually harassed.

"Both of these are fairly common and may appear benign — but together may create a power differential that leads to sexual harassment," Kundro said.

The team's findings on tipping back up those of previous nationwide surveys.

A 2018 report by the Restaurant Opportunities Center, a nonprofit group that advocates for better working conditions for restaurant workers, found that a majority of respondents who reported experiencing sexual harassment associated that harassment to their dependence on tips.

While women make up roughly half of restaurant employees overall, they are about two-thirds of tipped employees, who report sexual harassment at higher rates than their nontipped colleagues.

More than half of women in tipped jobs said depending on tips led them to accept behaviors that made them "nervous or uncomfortable," according to a 2014 survey from the group.

"By introducing many women to working life, the industry establishes cultural norms around sexual behavior that can shape perceptions of what's acceptable behavior in the workplace that workers carry with them long after they've left the restaurant industry," the 2018 Restaurant Opportunities Center report said.

Kundro said his study shows that restaurants can reduce sexual harassment for their employees by eliminating their dependence on tips or allowing them to perform their jobs without being required to smile.

"I think we really want organizations and managers to think carefully about their financial compensation models for employees and also their requirements for service with a smile," Kundro said.

Copyright 2021 NPR. To see more, visit https://www.npr.org.