To tip or not to tip... or should it be banned?
A New York restaurant has banned tipping to spare customers the bother, while some restaurants in other US cities have already replaced the gratuity with a fixed optional service charge. So is the discretionary tip falling out of favour in the land where it's king?
A young man and woman are sitting in a restaurant in New York, enjoying their second date.
The man pays the waiter the bill and heads to the bathroom while the woman gathers her things.
"How much did he tip?" she asks the waiter. He tells her.
When the man comes back to the table, there is an angry exchange and she says she doesn't want to see him again.
A tip of 8.5% brought that romance to a premature end.
This story, told years later by the waiter that night, Steve Dublanica, reflects both how seriously Americans take tipping and how loaded with social meaning it has become.
The size of tips has increased and the list of those who expect them is growing also, in recent years joined by staff in takeaways.
Meanwhile, tip jars have proliferated to such an extent you may be confronted by one where you receive your sandwich and another one a few feet away where you pay for it.
It's a custom that's become second nature for most Americans, although there's still a sharp intake of breath when they see three or four hotel staff involved in taking their luggage from the boot of the car and up to the room.
But it's worse for visitors - whom to tip and how much can be a source of debate, confusion and often anxiety at doing the wrong thing or appearing to be ungenerous.
Tip the barman but not the shop assistant, reward the hairdresser but not if he or she owns the salon. Give the hotel luggage guy a dollar or two but not the receptionist. And don't under-tip.
One British tourist says she and her friends were followed out of a Manhattan restaurant by an angry waiter unhappy with a 10-15% tip.
"The waiter gave us the tip back and told us it wasn't good enough, that as tourists we didn't understand that we had to give more in New York," says Janine Windust.
"One of my friends, a New Yorker, told him it was discretionary and not to be so rude, but the three Brits couldn't be bothered to argue and left him the full 20%.
"He chased us down the street, shouting 'I don't want it now, have it back!' Then there was a massive street argument over it."
That's an extreme reaction to what in the UK would be considered a reasonable tip, but some visitors to the US who leave no, or low, tips don't fully understand how critical they are to a worker's livelihood.
The federal minimum wage for tipped restaurant workers is $2.13 an hour, with tips expected to take the wage to $7.25 an hour.
"It was difficult and I lived and died by my tips," says Dublanica, who worked in New York restaurants for seven years and wrote a blog about it called Waiter Rant.
"If you don't tip, I can't pay the rent. But the reality is you can work hard and get no tips and do nothing and get good tips."
In the restaurant business, which accounts for about two-thirds of all tips paid in the US, there are signs of change.
Since last week, staff at Sushi Yasuda in New York have no need to worry about the generosity or tightfistedness of their customers.
Owner Scott Rosenberg has banned tipping, saying his staff already get a good wage, with benefits. He told The Price Hike he wants to improve the dining experience by eliminating the "math equation" from the end-of-meal ritual.
Other upmarket American restaurants have introduced an optional service charge of 15-20% instead of a tip. This is a common practice in the UK, usually between 10-15%.
This is a big issue in the hospitality industry now, says Dublanica, who adds he would support a service charge divided between employees if it helped to provide a proper wage and benefits such as sick pay. But he can't see it catching on.
"Even though the quality of service doesn't affect tipping, Americans are under the illusion they are tipping on service and like the illusion of being able to reward. They don't want to have that option taken away from them."
Tipping is an important custom, he believes, because it propagates the "American myth" that hard work brings reward.
But even Americans are not united in their support, with feelings that range from exasperation to outright resistance. The website Ban Tipping rallies around its central message: "We are educated consumers, and we do not tip. Deal with it."
One diner in California last year left a note in lieu of a tip and blamed an increase in sales tax.
In the memorable opening scene of the film, Reservoir Dogs, Mr Pink speaks for many when he questions why it is customary to tip some professions and not others.
Taking up this point, Lizzie Post, co-author of Emily Post's Etiquette, says it's customary to tip those who perform a service for you, although she acknowledges the inconsistency of rewarding the guy who moves your furniture but not the guy who cleans your clothes.
If drycleaners and others did get in on the action, the tipping economy would be even larger than it is now.
A man who has written 51 papers on the subject, Michael Lynn, of Cornell University School of Hotel Administration, estimates the tipping economy to be worth about $40bn (£25bn). That's more than twice the budget of Nasa.
But Lynn thinks tipping does imperceptible damage to collective well-being and he would like to see the custom outlawed in restaurants.
"It's a net drain on social welfare and our happiness. I think more people tip out of social obligation than tip because they want to, so people are parting with money they would rather keep.
"I don't know people are necessarily consciously aware of this. Most people would deny they tip for avoidance [of disapproval by peers and guilt], they say it's for good service, but I've looked at it and they don't reward good service substantially."
He also believes, based on his own research and other studies, that restaurant tipping is discriminatory, a system in which both black and white diners tip white servers more than black ones.
So he anticipates a class action brought by ethnic minority waiters and waitresses that could lead to tipping being declared illegal.
A service charge evenly divided between employees would head off any legal action. But that doesn't make economic sense, says Sherry Jarrell, a professor of economics at Wake Forest University and a former waitress.
"I think that customers will see the service charge as, firstly, a price increase on the food bill, secondly, a disincentive for using tipping to incent superior waitressing.
"To the extent it destroys a waiter's incentive to earn a high tip, it's harmful," she says. "I see very little economic behaviour or results that is improved by the move. All cost, no benefit."
Resistance to change would come from plenty of restaurant staff who make more money from tips than they would from the share of a service charge.
And customers wouldn't welcome it either, says Curt Gathje, lead editor at Zagat, who says it's so ingrained in the dining experience that it would be a difficult habit for many people to unlearn.
So a ban seems a long way off but there was a time when tipping was widely frowned upon in the US. Six states even outlawed it.
The custom arrived in the US from Europe in the late 1800s but early in the 20th Century, an anti-tipping campaign gathered pace, driven by the view it was undemocratic and a means to create a servant class.
"Tipping, and the aristocratic idea it exemplifies, is what we left Europe to escape," wrote William Rufus Scott in 1916.
His anti-tipping manual, The Itching Palm, went on: "In a republic where all men were supposed to be equal, some cannot be superior until they grind other men into dust. Tipping comes into a democracy to provide that relation."
Washington was the first state to ban it in 1909, followed by Arkansas, Iowa, South Carolina, Tennessee and Georgia. But these laws were all repealed by 1926, and since then tipping has flourished.
Now the US is probably the most tip-friendly country on earth, says Ofer Azar, a professor of behavioural economics at Ben-Gurion University of the Negev, Israel, but there are huge international variations.
"Tipping can be problematic because it seems to create classes, that of the customers, and that of the service workers, who have to satisfy the customers and sort of 'beg' for the tips," he says.
That is part of the reason why tipping wasn't allowed in communist USSR and China, and still isn't common in Scandinavia, he says - places where inequality was or is relatively low.
For those Americans who really want to avoid it, another international study offers some non-tipping havens they can escape to.
Mark Starbuck spent 10 years writing an unpublished thesis on tipping, in which he identified only four African countries that commonly practise it - Egypt, Morocco, South Africa and Tunisia.
In Singapore, tips are supposedly illegal, he found, while in Fiji, Iceland and Japan, they cause embarrassment and offence.
Here is a selection of readers' tipping nightmares and fairytales.