After the Sept. 11 attacks, Osama bin Laden vowed to bleed "America to the point of bankruptcy, Allah willing." If that was the plan, it didn't work. The years immediately following the attacks barely showed a blip of stagnation. A year out, unemployment was a calm 5.7%. Gross domestic product rose swiftly, as did consumer spending. Stocks regained pre-crisis levels within two months. Above all, the human toll of the nearly 3,000 who perished was unspeakable. And the cost of two ensuing wars is in the trillions. But in terms of our ability to innovate, produce, and achieve, bin Laden's goal of bleeding the nation bankrupt never stood a chance.  

Still, 9/11 changed how people think, particularly about risk. Here are a few lessons I've thought about lately.

There's a history of things that never happened
Hours after Pearl Harbor was attacked in 1941, the U.S. military planted mines in San Francisco Bay. Trenches were dug along the West Coast. President Roosevelt allegedly discussed a land invasion reaching as far inland as Chicago. The thought that Japan would follow up with an even greater attack on the mainland wasn't if, but when.

A similar attitude prevailed after 9/11. Everyone from policymakers to intelligence officials to lay Americans warned that an impending second attack was nearly certain. The media even gave it a name: The Age of Terror.

Save for the anthrax episode, we've so far avoided it in America -- and thank goodness.

Looking back, there's something to be said about feelings of inevitability that never come to pass. The fact that we experienced a terrorist attack that no one expected, and then avoided one that everyone did expect, is a strong lesson in how unpredictable the future is.

Emotion trumps rationality
In the year after 9/11, air travel fell and car travel jumped. Understandably, people suddenly thought planes were more dangerous than cars.

But statistically, the opposite is true. German professor Gerd Gigerenzer estimates that the increase in automobile travel in the year after 9/11 resulted in 1,595 more traffic fatalities than would have otherwise occurred. In other words, more than half as many people died attempting to avoid another 9/11 than died in the actual attack. Add in the impact that stress had on our health, and the reaction to 9/11 may have been more deadly than the attack itself. "People jump from the frying pan into the fire," Gigerenzer said.

In his book The Science of Fear, Daniel Gardner takes it a step further. He notes that if there were a 9/11 every month for an entire year, the odds that you'd be killed by terrorists are one in 7,750. By comparison, the annual odds of dying in a traffic accident are one in 6,498.

There's an important lesson about risk in there that can apply to other sides of your life, including investing. Like those reacting to the fear of another terrorist attack, investors seeking to avoid perceived risk often put themselves in greater actual risk. In the 1980s, those who bought gold in an attempt to safeguard and preserve their assets from inflation ended up losing the vast majority of their money. While attempting to protect their wealth, untold amounts have been lost by those cashing out when markets sink, only to miss the rebound that invariably follows. Risk can be an ironic foe.

"History doesn't crawl; it leaps."
Nassim Taleb made this point in his book The Black Swan. Societies "go from fracture to fracture, with a few vibrations in between," he wrote. "Yet we like to believe in the predictable, small incremental progression." This is the basis of Taleb's black swans: The unexpected shapes our lives in ways that the expected can't fathom.  

I've spent some time digging through archives in search of a 10-year economic forecast that fared accurate in hindsight -- or was accurate for the right reasons. No luck yet. In 1980, many worried that the world would soon run out of oil. Very few predicted the looming collapse of the Soviet Union. In 1990, most thought the housing slump resigned the economy to mediocrity. Almost none predicted an impending Internet boom. In 2000, most predicted that the national debt would be paid off within a decade. None knew Lehman Brothers would go bankrupt. None knew that a group of terrorists was plotting to strike America.

Most of what was expected to shape the past 30 years never happened, and what did shape the past 30 years was never expected. That's how it's always been, and the same will be true going forward. The events that will have the greatest impact on the next 30 years simply cannot be predicted today, will hit quickly, and will come out of nowhere. Sept. 11 reinforced that point. History doesn't crawl; it leaps.

Onward
The day after the attacks, Motley Fool co-founder David Gardner penned an article titled "The Day After." "I heard many say on Tuesday, 'The world will be forever changed,'" he wrote. "No more this. No more that. I certainly hope not. But this Wednesday morning I hear even more saying: 'Let's show them the spirit of America. Business as usual. If you stop doing, acting, creating, you've done just what the terrorists would like.'"

Sept. 11 did forever change the world. It took almost 3,000 Americans. It changed how we think. It changed how we plan. But it did not, as David wrote 10 years ago, stop us from doing, acting, and creating. Pause today to remember and honor the victims of the attack -- and the enduring spirit of America.