The percentage of the total undiscounted cost of the service, and what it says to your provider:

• 0% — “I forgot to tip/ I am from a foreign country and don't know to tip.”
• 10% or less — “My purse strings are extremely tight / I can barely afford the cost of the service / I am really dissatisfied with the service / I am kind of insulting you.”
• 15% — “The service was ok."
• 20% — “Thank you for your hard work and skill! The service was great."
• 20-25% — “I can tell you really went the extra mile, and I appreciate it.”

When you stop to think about it, the number of people you're expected to tip is a bit overwhelming:
Your bartender, table server, doorman, hotel bellman, coat room attendant, taxi driver, tour guide, pizza delivery guy, hair stylist, manicurist, massage therapist, body waxer — that guy who plays Jamaican steel drums in the subway station — all often go home without minimum wages if you don't dig into your own pocket.

So if you're someone who tips 10% (or less) both at the restaurant and the salon/spa, it may be time to update your thinking.

According to Groupon¹ and CNN’s Expert Guide², 15 to 20% is now the average tip amount for satisfactory-to-great service at a restaurant, while licensed personal service providers — like cosmetologists and massage therapists — receive 20 to 25%, according to a poll conducted by Aveda and published by NBC News³.

Why the difference, exactly?

Gabby C. is a licensed massage therapist with an upscale health club in Chicago who took a few moments to tell us about some of the extra costs of being a salon/spa professional. 

“I have to renew my license once every two years,” said Gabby. “And I’m required to get at least 24 continuing education credit hours within those two years to keep my license current and to build my skills. Classes can cost at least $100, depending on how many hours the class is worth.”
On top re-licensing and continuing education costs, stylists and salon workers often belong to professional organizations and associations, which are integral in providing networking opportunities, continuing education, training and more.

“I belong to the Associated Bodywork and Massage Professionals,” said Gabby. “My dues are $200 a year. That's the cheapest account that offers insurance. Some companies do deduct from your earnings to cover liability insurance, but in the state of Illinois we are required to also have personal liability insurance.”

“Everyone has their own out-of-pocket cost of living, but exceptional personal upkeep is so important in this industry,” added Gabby. “I take a vitamin regimen and get manicures regularly to insure my nail health because I don't want to give or get bacteria to and from my clients. I once massaged a client who failed to tell me they had pneumonia.”

“It can be pretty expensive to maintain a career in a salon or spa environment,” she concluded. “But you do it because you love it.” 
So the next time you visit the salon or spa, remember: a skimpy tip for your stylist, masseur, etc. may be considered an insult and may affect the quality of your service in the future.

1 Groupon: https://www.groupon.com/articles/guide-to-spa-and-salon-tipping-etiquette

2 CNN: http://www.cnn.com/2015/03/02/travel/experts-guide-to-tipping-in-the-united-states/

3 NBC News: http://www.today.com/style/hair-salon-etiquette-how-much-should-you-tip-your-hairstylist-t73331