From the book 'Jewish Humor' by Rabbi Joseph Telushkin:
In the early 1900s, an old Jew is traveling alone in his compartment on the Trans-Siberian Railroad. The train stopped and an officer in the czar's army got on. He and the Jew traveled for a while in silence. Suddenly, the officer grabbed the Jew by the lapels and demanded: "Tell me, why are you Jews so much smarter than everyone else?"
The Jew was silent for a moment, then responds: "It is because of all the herring that we eat." The officer quieted down and the trip resumed. Soon after, the Jew took out a piece of herring and started to eat it. The officer asked him: "How many more pieces of herring do you have?"
"A dozen", replied the Jew.
"How much do you want for them?"
"Twenty rubles", a big sum of money.
The officer took out the money and gave it to the Jew in exchange for the herring. After taking a few bites, the officer blurted out: "This is ridiculous, in Moscow I could have bought all of this herring for a few kopecks."
"You see", said the old Jew, "it's working already."
Thanks to my kiddush buddy Isaac P. for sending this!!