Two Ph.D. candidates, Bob and Joe, in the economics department often spent their afternoons debating economic theory. In preparing their dissertations, they consistently tried to outdo each other and solve the present economic crisis.

One day, after having an argumentative lunch as usual, the two went out for a walk, and to continue their debate on some theorem in econometrics. Joe suddently stopped walking. Bob casts a glance around and found what stopped Joe in his tracks. In front of them, on the sidewalk, is a pile of dog droppings.

Joe said to Bob, "I'll give you five hundred thousand dollars if you eat that."

Bob thought for a while, pulled out a pencil and a notepad, and did some calculation. After about 5 minutes, he proudly announced, "According to my economic theory, the marginal benefit of your offer far outweighs the marginal cost of my eating that, so I'll do it." And he gulps down the pile of dog droppings.

Silently, Joe wrote a check for the stated amount and handed it to Bob.

They continue their walk and their debate, albeit now Joe tends to avoid facing Bob directly because, well, of his breath. Suddenly, Bob sees another pile of dog droppings on the side walk. Thinking about what he just ate, he felt like throwing up. Joe on the other hand, was reminded of how he so easily lost most of his savings from his summer jobs on Wall Street.

So when Bob said to Joe, "You eat it, same offer," Joe immediately pulled out his paper and pencil and computed. After about three minutes of work, he patted Bob on the back, and announced that despite their theoretical differences, the conclusion is the same.

And so Joe wolfed down the steaming pile and Bob returned the check to him.

So now Joe is relatively happy for recovering his savings, and Bob is relatively happy because, well, at least now the two of them are even: each ate a pile of...

"Wait a minute!" Both of them exclaimed at once. They suddenly realized that neither of them gained anything, and each ate a pile of droppings. With tears streaming down their eyes, they went to their advisor to figure out what is wrong with their economic theories.

Their advisor patiently heard his two students describe the afternoon, and he started laughing and crying and shaking his head in excitement.

"Eureka!" He shouted, and he grabbed his students by the shoulder, shaking uncontrollably, "My dear students! Have you no idea what you just discovered? No? I hereby thank you on behalf of our beloved country. The two of you increased our national GDP by 1 million dollars by merely eating a couple piles of shit!"

I can only credit the joke to my mother, who forwarded to me the e-mail.