Women working in service jobs are more likely to be sexually harassed by customers if tipping is an option, new research has found.
And the more reliant the woman is on tips to make a living, the worse it is - especially if their bosses require them to always be friendly.
"Our findings highlight a really problematic - and previously unexplored - cost of tipping norms within service organisations," said University of Notre Dame researcher Timothy Kundro, who led the research.
Previous studies have found service workers frequently experience sexual harassment, but this one squarely links it to tipping culture - where staff are paid a poor base rate and expected to top it up with voluntary tips from customers.
"We were interested in understanding why sexual harassment is so pervasive in this context, and curious if any of these insights could provide actionable insights for organisations," said Dr Kundro.
Ninety-two full-time waitresses took part in the first half of the research, recording how much sexual harassment they were subjected to, how financially reliant they were on tips, how friendly they had to be and what power they felt customers had over them.
The results showed the more reliant workers are on tips and friendlier their bosses expect them to be, the more likely they are to be sexually harassed.
The second half of the study saw 229 men randomly assigned to four different restaurants - "one in which the waitress appeared friendly and dependent on tips, friendly and not dependent on tips, neutral and dependent on tips, or neutral and not dependent on tips". The results backed up the waitresses' experiences.
"Customers may not be thinking about how the employee depends on their tips for income, until they see that smile as an expression of deference, which suggests a low likelihood that they will resist or report unwanted advances," said co-author Pennsylvania State University professor Alicia Grandey.
Tipping is not common in New Zealand, where minimum wages are typically much higher than in the US, where it is widespread.
"It may not be necessary to completely eliminate customer tips, but rather reduce the dependence on tips by offering a livable wage," said Dr Grandey.
"Based on our results, if employees were less dependent on customer tips, harassment would be less likely to occur because customers would hold less power over the employee."
The study was published in the Journal of Applied Psychology on Tuesday (NZ time).