Attacking Problems

What tactics can stop suicide bombers? How should the nation respond to a potential bio-terror attack? Do needle exchange programs effectively reduce the spread of HIV?

Edward H. Kaplan, the William N. and Marie A. Beach Professor of Management Sciences, has studied each of these questions. Though the details of the problems vary drastically, Kaplan approaches them with the tools of an operations researcher, including mathematical and statistical models. “It’s this idea of paying attention systematically to what people are actually doing,” he says to describe his approach.

One other factor unites all of these problems. As Kaplan says, “I like to work on problems that other people care about.”


The problem: How to respond to a bio-terror attack

In 2002, Kaplan was asked by the National Institutes of Health to analyze how the country could best respond to a terror attack that used smallpox as a weapon. “Most of the work that had been done up to that point focused on what smallpox would do to people, and we turned it around and said, really, we’re interested in what we can do to smallpox.”

Kaplan looked closely at the logistics of the response effort. The smallpox vaccine can prevent the onset of the disease after an individual is exposed, if it is given within a limited window of time. The federal government’s plan called for the isolation of people with smallpox and targeted vaccination of only the people who had been in direct contact with the infected individuals. Kaplan and his team called the effort to track down all exposed individuals and administer the vaccine “the race to trace.” He says, “The race to trace was exactly the question, What’s the likelihood that you would find and vaccinate a person during the window period, given the resources that you’re putting into it? We concluded that actually winning this race would be very hard and if there was a large-scale outbreak, it would be much more sensible to just try to raise immunity in the population as quickly as possible [by vaccinating more widely].”

The problem: How to stop suicide bomber attacks

When Kaplan turned to analyze the problem of suicide bombings in Israel, he found that most studies of the issue gathered tremendous amounts of detail about each known attack, from where the attacker lived to how many brothers and sisters the attacker had.

Kaplan took a different approach: “The basic question should be, how can we stop them? That led me to a study with some Israeli co-authors of which counter-tactics are effective and which ones aren’t. And in order to do a study like this, you need to know what’s going on all the time, not just on the days when the bombings occur. You need to know what’s going on every day.”

Kaplan compiled data on both the attacks themselves and on the counter-terror tactics being employed by the Israeli government -- for days when there were attacks and for days when there weren’t any attacks. He and his colleagues developed statistical models that relate Israeli counter-actions to suicide bombing attempts to determine if such tactics led to fewer attacks.

Various observations and conclusions have emerged from this wide-ranging study. Kaplan points to one example: “As the actual number of suicide bombing attempts increases, the chance of catching any one of them increases.” Such findings have implications for the strategic approach each side is likely to take. Kaplan also found that preventive arrests seemed to be a more effective tactic than targeted killings.

Kaplan has also studied how to respond in the seconds before a suicide bomb attack. “Let’s say you’re in a shopping mall or on the street and it turns out that a suicide bomber is about to explode,” says Kaplan. “Is it better or worse if there are more versus fewer civilians right around the area where the bomber’s going to blow up? Your first thought would be, ‘Well, the more people there are, the more people are going to get killed.’ But it actually turns out that that’s not true.” Kaplan explains that in a densely packed crowd, the people closest to the bomber will absorb much of the shrapnel from the explosion, shielding those standing behind them. In a sparser crowd, the shrapnel will spread out, hitting more people.

This analysis leads Kaplan to conclude that last-minute responses to a suicide bomber, such as telling people to run or duck, are likely to be counterproductive. Says Kaplan, “You want to try to stop bombers before they get started. So, that says you want to push most of your effort into intelligence.” (A paper Kaplan wrote on this issue recently received the Koopman Prize for the outstanding publication in military operations research of the previous year. He had previously received the award for a paper on the smallpox issue.)

The problem: How to win an NCAA Basketball Tournament pool

Every March millions of people compete in pools in which they try to pick the winners of every game in the NCAA Basketball Championship Tournament. Kaplan and SOM Deputy Dean Stanley J. Garstka decided to look more closely at how these pools work. Says Kaplan, “We had goofed around with these pools at home and we never did very well. And we said, ‘Wait a minute, this is a great operations research problem because you’ve got a very specific objective and you’ve got very well defined rules and there’s a lot of data out there.’”

Kaplan points out that many people pick the team that they think will win each game, fill out a bracket, and then submit the same bracket to a variety of pools. However, different pools have different rules, such as awarding extra points for picking an upset or for getting late-round matchups right. Kaplan and Garstka found that success in tournament pools depends as much on understanding the rules of the pool as on being able to predict winners. “That’s the thing that operations researchers focus on that a lot of people don’t: How is the system actually going to work?” says Kaplan.

The problem: How to determine whether needle exchange programs work

In the late 1980s needle exchange programs were a controversial approach to slowing the
spread of HIV. In such programs, intravenous drug users could exchange used needles for new ones. The hope was that this would lead to fewer addicts injecting with used needles and getting infected with HIV. However, the programs were also controversial, with some arguing that they contributed to increased drug use.

When Kaplan started looking at the issue of whether these programs were effective, he says that previous studies had interviewed drug users to determine if they changed their behavior. “Public officers and policy people didn’t find those results credible…. My insight was that you could learn a lot about this, not by interviewing the people, but by interviewing the needles.”

Kaplan and his colleagues studied a needle exchange program in New Haven, Connecticut. They assigned every needle a unique identifying number and tracked it. “We knew when it went out, when it came back, if the person who brought it back was the same as the person who received it, and, for a subset of the needles, whether or not they were infected.”

With this data, Kaplan developed a mathematical model to analyze the program’s effect on transmission of the disease. “We used models similar to models for Malaria, where you have people infecting mosquitoes and mosquitoes infecting people. With HIV among drug users, you have people infecting needles and needles infecting people.”

The result of his study: “The length of time the needles were in circulation would go down, so the opportunities for them being reused would go down, so the fraction infected would go down, so the rate of new infections would go down. This was all easily seen in the data.”

Kaplan’s work on this issue convinced the policy makers that needle exchange programs work. The New Haven program he studied was granted additional funding and duplicated in other cities around the country.


Kaplan’s most recent published paper looked at anti-Israel statements and anti-Semitism. “Many argue whether or not the language used by those expressing extreme criticism of Israel is anti-Semitic,” says Kaplan. But he decided to test the proposition. Treating extreme anti-Israel statements as data in a survey of 5,000 Europeans, he used operations research models to estimate the probability that a person agreeing with such statements also subscribes to long-standing anti-Semitic canards, such as Jews cheat in business. The result: the stronger the degree of anti-Israel sentiment observed, the more likely that the person making such statements agrees with anti-Semitic stereotypes.

Kaplan is also working on several ongoing problems, such as how to estimate current HIV incidence in the U.S. He is serving on a National Academy of Sciences panel on defeating improvised explosive devices, and he continues to develop his strategic analysis of suicide bombing and counter-tactics in the Israeli- Palestinian conflict.

Looking over his disparate oeuvre, Kaplan says, “Most of my interest actually tends to be in problems which involve making things better off, often in the form of saving lives… In that sense, counter-suicide bombing and needle exchange actually have a lot in common. These are all very serious problems, maybe with the exception of the basketball.” He thinks about it for a moment and adds, “Some people would think that’s the most serious problem.”