Do you always tip your driver after an Uber ride? If you do, you are in a seriously small minority, according to new research.

A study published by the National Bureau of Economic Research, based on four weeks of experience in the field and data from millions of Uber trips, found that only 16 percent of Uber rides result in a tip to the driver.

A scant 1 percent of riders give the driver a tip every time, the study said, while 60 percent never tip at all. Riders not included in those two groups only provide a tip on about one of every four rides.

Of those who do tip, the average amount is $3.11 per ride, or roughly 26 percent of the fare. “Tips tend to be highest for airport trips and business trips,” the study notes (i.e., when costs are likely to be reimbursed by a traveler’s employer), and tipping is more common for rides in smaller cities than in large ones.

One of the researchers involved in the project told The Verge that the relatively low level of tipping is likely a product of Uber’s app-based tipping procedure. Unlike traditional taxi trips, where the rider pays and tips the driver in a face-to-face transaction at the end of the ride, an Uber rider isn’t asked by the app whether he wants to tip the driver until after the ride is over and he has exited the vehicle.

TAKE OUR POLL about tipping here or at the bottom of the page.

The study turned up other differences between riders in their tipping habits. For instance, men who tip the driver give him or her 23 percent more than female riders who tip, on average. And both men and women tippers give female drivers 10 to 11 percent more than they give male drivers. (“However, the tip premium that male riders pay to female drivers falls with the driver’s age and disappears by the age of 65,” the study notes.)

What’s more, riders who hold a five-star rating in the Uber app are twice as likely to tip their driver as a rider with a 4.75 rating, and they tend to give the driver 14 percent more. Conversely, Uber drivers with a five-star rating are 50 percent more likely to be tipped than those rated 4.75.

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As you might expect, the quality of the rider’s experience also affects tipping: “Leveraging telematics data from drivers’ phones, we find that quick accelerations, hard brakes, and speeding are all associated with lower tip levels. Similarly, not meeting estimated pick-up times lowers tips,” the study said.

Tipping has long been a sore point between Uber and its drivers, even though rival Lyft has allowed the practice for years. Uber was originally vague about the subject of tipping, suggesting that it was included in the fare. In a 2016 settlement of class action lawsuits filed by drivers, the company agreed to inform riders that tipping is not included in the fare – but also that it was neither expected nor required.

It wasn’t until the summer of 2017 that Uber started updating its app to allow for riders to add a tip to the fare. In addition to demands from its drivers, Uber also faced pressure from some municipalities to include a tipping option.

So I'm wondering... are frequent travelers better tippers? Do YOU tip your Uber or Lyft drivers? Answer our poll and let's see how TravelSkills on SFGATE readers compare:

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Chris McGinnis is the founder of TravelSkills.com. The author is solely responsible for the content above, and it is used here by permission. You can reach Chris at chris@travelskills.com or on Twitter @cjmcginnis.