The economists who carried out the mischievous research have quantified the difference between the cost of a present and its monetary worth to the recipient.

They found that, on average, those receiving a present thought it was worth 16% less than its price in the shops. They conclude that people should give cash and let recipients buy their own gifts.

In a provocative definition that would surely have been appreciated by Scrooge, the economists have called the difference in values "the deadweight cost of Christmas".

With Britain's shoppers midway through what is expected to be a record £30 billion December spending spree, Joel Waldfogel, an economist at the University of Pennsylvania who carried out the research, says in his study: "Consumers prefer items they choose for themselves to items chosen for them by others . . . We confirm that gift-giving is an inefficient means of allocating resources." Waldfogel has calculated that Americans spend £6 billion too much on presents.

The research, which asked people to place monetary values on their presents from last Christmas, told them to exclude sentimental considerations, which psychologists claim are the key to a gift's true "value".

The most "efficient" present givers, in which the difference in values was lowest, were spouses or lovers. They were followed by grandparents, who were ahead of parents, siblings and friends. Presents from aunts and uncles were the most undervalued by the recipients.

Consumer analysts believed spouses and lovers might know each other better and even choose presents together. Grandparents might benefit from the fact that they may be more likely to choose cash, tokens or practical gifts.

Stephen Lea, a psychology professor at Exeter University, said only an economist would value a gift purely on its monetary worth.

"The study seems to have missed the point of Christmas. The only time in my career I have ever been threatened with violence was when I pushed someone to explain why they didn't just give their mother cash as a gift," he said.

"The closer the relationship, the less important is the value. A gift can be cheap and valued or expensive and wrong."

Shoppers buying Christmas presents this weekend partially confirmed the economists' league of successful gift buyers. Claire Millard, 20, a student shopping in Birmingham, said: "The worst present I ever got was a big pair of pants from my auntie."

Michael Sheldon, 23, a waiter who was shopping in London's West End, said: "A couple of years ago my mum got me an Everton football shirt for Christmas, but I'm a Liverpool supporter. I couldn't believe it."

George Standley, 53, a business manager from Birmingham, said: "The best present I ever received was when my wife gave me a ticket to go with her to Africa. It's always nice to know that someone is thinking about you."

The economists who wrote the study say travel tickets and clothes tended to be the gifts most undervalued by their recipients, as well as art.

Keith Wilkins, 42, from Guildford in Surrey, disagreed. "It sounds like these economists have completely missed the point. My daughter could draw me a picture which would be worthless to an academic but invaluable to me. They need to study the real world," he said.

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