When two people each have items the other wants, both people can determine the values of the items and provide the amount that results in an optimal allocation of resources. Therefore, if an individual has 20 pounds of rice that he values at $10, he can exchange it with another individual who needs rice and who has something that the individual wants that's valued at $10. A person can also exchange an item for something that the individual does not need because there is a ready market to dispose of that item.
However, this isn’t always possible. For instance, you may have a $150 digital music player and want a small refrigerator worth $100. In this case, if both parties are certain of what they want and understand the difference in value, there should be no barterer’s remorse. Alternatively, you can ask for the mini-fridge plus $50 to make the trade – the worst anyone can say is “no.”
Economists since the times of Adam Smith (1723-1790), looking at non-specific pre-modern societies as examples, have used the inefficiency of barter to explain the emergence of money, of "the" economy, and hence of the discipline of economics itself. However, ethnographic studies have shown that no present or past society has used barter without any other medium of exchange or measurement, nor have anthropologists found evidence that money emerged from barter, instead finding that gift-giving (credit extended on a personal basis with an inter-personal balance maintained over the long term) was the most usual means of exchange of goods and services.
Since the 1830s, direct barter in western market economies has been aided by exchanges which frequently utilize alternative currencies based on the labor theory of value, and designed to prevent profit taking by intermediators. Examples include the Owenite socialists, the Cincinnati Time store, and more recently Ithaca HOURS (Time banking) and the LETS system.
It was the fifth lasagna that did it. Three months into the project, Simmons had signed up over 80 Barter Babes, and every time she bartered her financial services, she seemed to get a lasagna in return. She was trying to shove yet another five-pound pasta dish into her freezer when the tears started to flow. “I don’t need another lasagna!” she yelled at her boyfriend. “I need a haircut! I need a bicycle!” She was overwhelmed with doubts about her bartering experiment: I’m so ridiculous. What the hell was I thinking? This whole thing is never going to work. Trades weren’t happening at the frequency she had anticipated, and Simmons was feeling depressed. She couldn’t afford a dye job at a salon, and she had started gaining weight. She’d gone from ballin’ to having $200 in her joint account.