The bubble, as investing phenomenon, has been well studied ever since the 17th-century tulip frenzy. Its counterpart in bear markets is not well understood.

There are no good or bad stocks. The company is either good or bad. Stocks are just stocks.

Indeed, bull markets are fueled by successive waves of prior skeptics finally capitulating as their fears fade. Eventually, fear turns to euphoria, and that's the stuff of bubbles.

The bubble, as investing phenomenon, has been well studied ever since the 17th-century tulip bulb frenzy. Its counterpart in bear markets is not well understood.

Bulls don't read. Bears read financial history. As markets fall to bits, the bears dust off the Dutch tulip mania of 1637, the Banque Royale of 1719-20, the railway speculation of the 1840s, the great crash of 1929.

I've long loved emerging markets airlines because they usually sell at bargain prices. The troubled history of developed market airlines unfairly taints these stocks. In the emerging world, they're growth stocks.