A tip jar sits on an ice cream truck at the display of Republican presidential candidate Michigan Congressman Thaddeus McCotter at the Iowa Straw Poll on August 13, 2011 in Ames, Iowa. - 

The holidays provide a chance for us to show our appreciation for the people we've done business with throughout the year. Giving a little something extra to the hair dressers, mail carriers, housekeepers and doormen is part of our society's code of etiquette. The spirit of generosity is remarkable this time of year, especially to the people who rely heavily on tips to supplement their incomes.      

Tipping is a way to say thanks to someone who has made your life a little easier. It creates a personal connection, even if just for a moment. And indeed, tipping is all about relationships.

Holona Ochs is an assistant professor of political science at Lehigh University and an expert on America's tipping industry and she says tipping may be more about emotions than economics.

"Individually whether or not somebody can identify with the person that they are tipping, whether or not the person that is receiving the tip feels that they can make a connection...these things affect not only the size of the tip, the regularity of the tipping, but also how people experience the norm of tipping itself," says Ochs.

According to Ochs, the U.S. tips more money, more often than any other country. More than 90 percent of Americans tip, and if it feels like more and more occupational categories are recieving tips these days, that's because they are. Ochs notes that teachers in wealthy school districts are more likely to get a tip nowadays.

In her work, Ochs has found that the tip amount more often reflects on the tipper than the tippee's service.

"Tipping does not serve as a clear signal about the quality of service and it doesn't serve a monitoring function," says Ochs. "In the strictest economic sense it doesn't have an economic purpose. It's an emotionally and culturally driven practice."