The Sky Isn't Falling -- Yet.(Global Investor)

Byline: Ruchir Sharma; Sharma is head of emerging markets at Morgan Stanley Investment Management.

Bubbles tend to peak when stock prices reach 50 to 60 times projected earnings. China's domestic market is around 35.

With global financial markets in the midst of another panic attack, investors would do well to consider the calming words of that beloved children's character -- and overlooked philosopher -- Winnie the Pooh. In response to the frantic question "What if the sky falls on us?" Pooh turns around, smiles and says: "What if it doesn't?" At this advanced stage of a bull market, investors typically have a rather sanguine view of the world.

Yet a remarkable feature of the current bull market in global stocks -- one of the longest and most powerful in history -- is that financial analysts are spending more time worrying about unwelcome developments that could end the party than basking in the upswing. This year the concerns revolve largely around the woes of the U.S. credit market, but in the past few years there has always been something to fray nerves in the marketplace, from high commodity prices to the U.S. current-account deficit.

Through it all, the bull market has climbed one wall of worry after another, with the global economy reveling in its best spell in postwar history. That hasn't stopped the financial commentariat from fretting. They now worry that the interest-rate cuts by the Federal Reserve are doing little to boost a debt-laden U.S. economy, but are instead creating bubbles in other parts of the world, including in the superhot stock market in China. Given these ongoing concerns about the fragility of the bull-run, it's worth examining what could in fact bring about an end to this bull market -- and what could not.

For one, bull markets don't just die of old age. A catalyst is required to precipitate a downturn, and historically, only one factor has terminated bull runs: rapidly rising interest rates. Bear markets occur when earnings collapse due to an economic recession, which in turn is brought about when real interest rates cross the threshold of pain. From the Great Depression of the 1930s to the East Asian crisis of 1997-98, all major market declines have taken place against the backdrop of an aggressive monetary-policy stance. In developed economies, central banks raise rates aggressively when they are trying to contain inflation or attempting to prick an asset-market bubble. In emerging markets, central banks act for those two reasons and one other: in the past, they have often hiked rates to prevent their currencies from weakening. These days, key emerging markets are battling to keep their currencies from appreciating too rapidly.

So then the question, of course, is whether the central banks have any reason to get aggressive ...