No One Is Sure Where Terrorists Will Strike

First, some calculations, courtesy of Risk Management Solutions, a consulting firm that advises insurance companies on catastrophic risks:

The current terrorism risk in the United States is 0.5 events per year, or one event per 24 months.

If there is an attack, there's roughly a 50 percent chance that terrorists will employ conventional explosives. Intentional plane crashes, incendiary events and destruction of chemical depots, nuclear power plants or other industrial sites are less likely.

Least likely is the chance that the next attack will feature chemical, biological, radiological or nuclear weapons -- CBRN, in the trade. That is less than 10 percent.

Washington and New York City are at the top of the list of targets and in a category by themselves, RMS experts believe. A competing firm includes San Francisco in the first tier along with those two cities, but RMS sticks with Washington and New York alone.

Now, what can one say about these predictions?

Unquestionably, they are the product of laborious research, higher-order mathematics and hard-to-get expert opinion. But only time will tell whether they're right.

It's very difficult to say much about events that are exceedingly rare or, like many terrorist attack scenarios, haven't occurred even once. That's why almost every statement about terrorism and preparedness is swaddled in caveats.

Take a "dirty bomb," which does its damage by spreading radioactive dust. An explosion five blocks away is dangerous, but what about one five miles away?

"That's likely to be far enough away to avoid risk, but no one can make a categorical statement that it is far enough away to avoid risk," says Jonathan Links, a professor of environmental health sciences at Johns Hopkins University who is Baltimore's consultant on radiological terrorism.

A similar observation -- with details and distances changed -- holds for just about every other hazard.

Besides the federal government, the insurance industry is the one sector of American life that can't get around attempting rational estimates of terrorism risk. It must, in order to offer -- and price -- terrorism insurance. Insurance companies' exposure is enormous; the payouts from the Sept. 11, 2001, attacks are expected to be $40.2 billion.

Three companies in the United States are engaged in modeling terrorism catastrophes. All have extensive experience in quantifying and predicting natural hazard risks. They are RMS, of Newark, Calif.; EQECAT, of Oakland, Calif., and Applied Insurance Research, of Boston.

These companies list more than 240,000 potential targets in the United States and model attacks on a relatively small percentage of them. The damage estimates and attack probabilities they come up with are generally secret, although a few facts trickle out. For example, California's share of the total national risk of an attack is 8.5 percent, according to an EQECAT estimate done for the Workers' Compensation Insurance Rating Bureau of California. (None of the companies was willing to say what Washington's share is.)

However, there seems to be a consensus that the likeliest targets are government offices; "trophy buildings" such as skyscrapers; hazardous industrial sites, and transportation facilities such as bridges and tunnels. They provide the possibility of a high-profile attack causing enormous life and property loss, which appear to be terrorist goals.

It logically follows that people living outside urban centers are at a lower risk of attack. That conclusion doesn't conflict with the very real possibility that terrorists may choose to strike at something like a Midwest state fair simply to be counterintuitive. Such a possibility, however, barely raises the low risk of Midwesterners compared to East Coast city dwellers, because there are many, many central U.S. targets with the same likelihood of being chosen, experts believe.

Gary Hart, the former senator and presidential candidate who is sounding a clarion call for greater terrorism preparedness, personally thinks such an attack is next.

"My belief is that it will involve multiple targets in the inland United States, and will probably involve biological agents," he said last week.

His source of information?

"Intuition," he said. "It is calculated by trying to get inside the mind of the terrorist."

-- David Brown
Washington Post Staff Writer