#48 Planet Money: North Korea's Hidden Market

When you arrive as a tourist in North Korea — yes, it's been done — they don't tell you the news, says Curtis Melvin. They tell you the state of the economy. And yes, they do have one. Melvin knows because it tracks it on his blog, North Korean Economy Watch. One of his biggest boosts comes from Google Earth, which lets him watch what passes for economic development.

And a look at the "efficient market" hypothesis, which helps to explain why, in the long haul, Jim Cramer and company fare as well as anyone else on Wall Street.