You can interpret Tuesday's worldwide stock market spasm as a tipping point, a signal that we're nearing the end of an economic era.

Or you can see it as proof that global financial markets are now all hardwired together in ways that make us all subject to the whims of the Chinese.

You can even build a narrative that ties it all back to former Fed Chairman Alan Greenspan, with the old lion proving that, even in retirement, he can still make the markets spin.

Yet at the end of the day, I suspect the message we'll take from Tuesday's pre-March madness is simply that markets move unpredictably. Always have, always will.

As a matter of fact, what struck many market gurus most about Tuesday's big move was how normal it was - in comparison with the weeks and months that preceded it.

Not that you see a drop of 416 points in the Dow Jones industrial average every week. In absolute numbers, it was the seventh-largest decline in the Dow's history. Even in percentage terms, 3.3 percent isn't something to sneeze at.

But what was really newsworthy about the mini-crash, or correction, or whatever you want to call it, was that it punctuated an unusually stable period.

Here's what I mean. The last time the Dow moved this much - up or down - was in October 2002.

Back then, the popular stock index bounced up 1,000 points in just a couple of days before beginning what has turned out to be a long, steady climb to its current level.

But as the bloggers at Birinyi Associates, a Wall Street research firm, remind us, it's the steady part that's the real anomaly. The last five years mark the fourth-longest stretch on record without a rise or fall of this magnitude.

This isn't the kind of Wall Street record that gets most people's attention. How could it be? By definition, there's nothing sexy or headline-worthy about quiet markets.

But among economists and professional market-watchers, what they call the lack of volatility has been a fairly big deal.

In recent months, some forecasters and fund managers have been like the old Western scout in those cowboy movies, who scowls at the horizon as he drawls: "It's too quiet out there - I don't like it."

The nonvolatile behavior of recent years was particularly suspicious when you consider some of the financial tensions that have been building up.

Some analysts, for instance, think long-term interest rates are abnormally low - lower than some short-term rates, in fact. Others say the value of the U.S. dollar is out of whack relative to the Japanese yen or Chinese renminbi.

The point is that there is plenty of risk out there - in real estate, in commodities, just about anywhere you look in the financial world.

Given all that, it would make sense for stock markets to be just a little bit jumpy. Jumpier, at any rate, than they have been for most of the last five years.

That's not to say the causes of Tuesday's sudden rout are uninteresting or irrelevant. It's fascinating that a sell-off in the Shanghai stock market rippled around the globe, causing shares to tumble in Europe and the United States in less than 24 hours.

Some, such as Morgan Stanley's Steve Roach, have wondered if the whole thing might have been part of some Chinese government effort to tame that country's wildfire speculation and keep its economy from overheating.

But I prefer the Greenspan thesis, since it reprises so neatly the famous "irrational exuberance" incident of 1996.

It was on Dec. 5 of that year, when the central-bank maestro uttered that phrase in a speech, touching off a one-day market panic.

The next day, all eyes turned to Philadelphia, where Greenspan was to speak at the Union League. Would he explain, amplify, elaborate?

Nope. Greenspan talked on a different subject, and stocks soon resumed soaring, on a ride that lasted three more years.

Contact Andrew Cassel at 215- 854-5981 or acassel@phillynews. com. Read his recent work at http://go.philly.com/andrewcassel.