Are you a Republican man from Connecticut paying for your meal with a credit card? You’re probably a great tipper, according to a new report from CreditCards.com.

The credit card information website teamed up with researchers from Princeton and surveyed about 1,000 adults across the U.S. Their study indicates that the best tippers are men, Republicans, from the Northeast, and customers paying with a credit or debit card. These groups generally tip a median of 20% when dining at a restaurant.

The study says that women, Democrats, Southerners, and those paying in cash leave a 15% to 16% tip, on average.

Why are some groups better tippers than others?

"Generally it all comes down to income," said Matt Schulz, senior analyst at CreditCards.com. "The more money you have the more likely you are to leave a little extra tip on the table."

Tipping etiquette can spark hot debate. The etiquette experts at the Emily Post Institute recommends diners tip at least 15% to 20% pre-tax at a sit-down restaurant.

About half of tippers in the survey fell into that sweet spot, tipping between 16% and 20%. On the low end, one-in-five customers at dine-in restaurants don’t leave any gratuity at all.

“I was definitely surprised by how many people tip over 15%, but I was also surprised by how many people never tip at all at a restaurant,” said Schulz..

“How is that even possible? I’m guessing they don't get very good service on their next visit,” he said.

More:Diners leave waitress taunting note and no tip

Tipping: There's no guarantee

Tipping is a cultural norm in America and those tips are how many people pay the bills. In most states, tipped workers generally make about $2.13 per hour as base pay and the rest of their salary comes in the form of tips, according to government data, with many having to split tips with other restaurant staff.

Tipped workers make the federal minimum wage, before gratuities, in just nine states: Alaska, California, Hawaii, Minnesota, Montana, Nevada, New York, Oregon and Washington.

Waitstaff are dependent on the goodwill of their customers for their salary, according to Teofilo Reyes, of Restaurant Opportunities Center United, an organization that advocates for restaurant workers.

“Tips can vary pretty dramatically, so there’s no stability in wages from tipping.” Reyes said. “There’s no guarantee that someone’s going to tip you.”

Rayes said tipping is really dependent on the personality of the customer and can be based on a lot more factors than just service, like race. A 2008 study conducted by Michael Lynn, a professor at Cornell University, found that both black and white customers tip black servers less than their white counterparts.

Payscale, an online salary database, estimates that hourly tips can range from $1.01 to $16.16. Tips can account for 58% of a waiter’s salary, according to Payscale.

Although employers are required to pay tipped workers minimum wage after tips, in 2016 the food service industry owed employees almost $40 million in back pay.

Pay violations disproportionately impact women and people of color in the service industry. Seventy percent of servers are women, and a ROCU study found that 90% of women who rely on tips have experienced sexual harassment at work, both from managers and customers.

“The idea that 'the customer’s always right' becomes much more salient. You can’t stand up for yourself unless you’re willing to lose your wages,” said Reyes.

Some customers argue that instead of tipping, restaurants should simply pay workers a fair wage. In response, restaurants including upscale eateries like Per Se and The French Laundry have banned tipping altogether.

When Joe's Crab Shack experimented with eliminating tips, customers complained of higher food prices and poor service. Cornell's Lynn is unsure whether the quality of service actually decreased or the expectation of poorer service was enough to upset customers, but as a result, Joe's Crab Shack brought back tipping.

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