3.
A world that follows the rules of epidemics is a very different place from the world we think we live in now. Think, for a moment, about the concept of contagiousness. If I say that word to you, you think of colds and the flu or perhaps something very dangerous like HIV or Ebola. We have, in our minds, a very specific, biological notion of what contagiousness means. But if there can be epidemics of crime or epidemics of fashion, there must be all kinds of things just as contagious as viruses. Have you ever thought about yawning, for instance? Yawning is a surprisingly powerful act. Just because you read the word “yawning” in the previous two sentences—and the two additional “yawns” in this sentence—a good number of you will probably yawn within the next few minutes. Even as I’m writing this, I’ve yawned twice. If you’re reading this in a public place, and you’ve just yawned, chances are that a good proportion of everyone who saw you yawn is now yawning too, and a good proportion of the people watching the people who watched you yawn are now yawning as well, and on and on, in an ever widening, yawning circle.
Yawning is incredibly contagious. I made some of you reading this yawn simply by writing the word “yawn.” The people who yawned when they saw you yawn, meanwhile, were infected by the sight of you yawning—which is a second kind of contagion. They might even have yawned if they only heard you yawn, because yawning is also aurally contagious: if you play an audiotape of a yawn to blind people, they’ll yawn too. And finally, if you yawned as you read this, did the thought cross your mind—however unconsciously and fleetingly—that you might be tired? I suspect that for some of you it did, which means that yawns can also be emotionally contagious. Simply by writing the word, I can plant a feeling in your mind. Can the flu virus do that? Contagiousness, in other words, is an unexpected property of all kinds of things, and we have to remember that, if we are to recognize and diagnose epidemic change.
The second of the principles of epidemics—that little changes can somehow have big effects—is also a fairly radical notion. We are, as humans, heavily socialized to make a kind of rough approximation between cause and effect. If we want to communicate a strong emotion, if we want to convince someone that, say, we love them, we realize that we need to speak passionately and forthrightly. If we want to break bad news to someone, we lower our voices and choose our words carefully. We are trained to think that what goes into any transaction or relationship or system must be directly related, in intensity and dimension, to what comes out. Consider, for example, the following puzzle. I give you a large piece of paper, and I ask you to fold it over once, and then take that folded paper and fold it over again, and then again, and again, until you have refolded the original paper 50 times. How tall do you think the final stack is going to be? In answer to that question, most people will fold the sheet in their mind’s eye, and guess that the pile would be as thick as a phone book or, if they’re really courageous, they’ll say that it would be as tall as a refrigerator. But the real answer is that the height of the stack would approximate the distance to the sun. And if you folded it over one more time, the stack would be as high as the distance to the sun and back. This is an example of what in mathematics is called a geometric progression. Epidemics are another example of geometric progression: when a virus spreads through a population, it doubles and doubles again, until it has (figuratively) grown from a single sheet of paper all the way to the sun in fifty steps. As human beings we have a hard time with this kind of progression, because the end result—the effect—seems far out of proportion to the cause. To appreciate the power of epidemics, we have to abandon this expectation about proportionality. We need to prepare ourselves for the possibility that sometimes big changes follow from small events, and that sometimes these changes can happen very quickly.
This possibility of sudden change is at the center of the idea of the Tipping Point and might well be the hardest of all to accept. The expression first came into popular use in the 1970s to describe the flight to the suburbs of whites living in the older cities of the American Northeast. When the number of incoming African Americans in a particular neighborhood reached a certain point—20 percent, say—sociologists observed that the community would “tip”: most of the remaining whites would leave almost immediately. The Tipping Point is the moment of critical mass, the threshold, the boiling point. There was a Tipping Point for violent crime in New York in the early 1990s, and a Tipping Point for the reemergence of Hush Puppies, just as there is a Tipping Point for the introduction of any new technology. Sharp introduced the first low priced fax machine in 1984, and sold about 80,000 of those machines in the United States in that first year. For the next three years, businesses slowly and steadily bought more and more faxes, until, in 1987, enough people had faxes that it made sense for everyone to get a fax. Nineteen eighty seven was the fax machine Tipping Point. A million machines were sold that year, and by 1989 two million new machines had gone into operation. Cellular phones have followed the same trajectory. Through the 1990s, they got smaller and cheaper, and service got better until 1998, when the technology hit a Tipping Point and suddenly everyone had a cell phone. (For an explanation of the mathematics of Tipping Points, see the Endnotes.)
All epidemics have Tipping Points. Jonathan Crane, a sociologist at the University of Illinois, has looked at the effect the number of role models in a community—the professionals, managers, teachers whom the Census Bureau has defined as “high status”—has on the lives of teenagers in the same neighborhood. He found little difference in pregnancy rates or school drop out rates in neighborhoods of between 40 and 5 percent of high status workers. But when the number of profes sionals dropped below 5 percent, the problems exploded. For black schoolchildren, for example, as the percentage of high status workers falls just 2.2 percentage points—from 5.6 percent to 3.4 percent—drop out rates more than double. At the same Tipping Point, the rates of childbearing for teenaged girls—which barely move at all up to that point—nearly double. We assume, intuitively, that neighborhoods and social problems decline in some kind of steady progression. But sometimes they may not decline steadily at all; at the Tipping Point, schools can lose control of their students, and family life can disintegrate all at once.
I remember once as a child seeing our family’s puppy encounter snow for the first time. He was shocked and delighted and overwhelmed, wagging his tail nervously, sniffing about in this strange, fluffy substance, whimpering with the mystery of it all. It wasn’t much colder on the morning of his first snowfall than it had been the evening before. It might have been 34 degrees the previous evening, and now it was 31 degrees. Almost nothing had changed, in other words, yet—and this was the amazing thing—everything had changed. Rain had become something entirely different. Snow! We are all, at heart, gradualists, our expectations set by the steady passage of time. But the world of the Tipping Point is a place where the unexpected becomes expected,where radical change is more than possibility. It is—contrary to all our expectations—a certainty.
In pursuit of this radical idea, I’m going to take you to Baltimore, to learn from the epidemic of syphilis in that city. I’m going to introduce three fascinating kinds of people I call Mavens, Connectors, and Salesmen, who play a critical role in the word of mouth epidemics that dictate our tastes and trends and fashions. I’ll take you to the set of the children’s shows Sesame Street and Blue’s Clues and into the fascinating world of the man who helped to create the Columbia Record Club to look at how messages can be structured to have the maximum possible impact on all their audience. I’ll take you to a high tech company in Delaware to talk about the Tipping Points that govern group life and to the subways of New York City to understand how the crime epidemic was brought to an end there. The point of all of this is to answer two simple questions that lie at the heart of what we would all like to accomplish as educators, parents, marketers, business people, and policymakers. Why is it that some ideas or behaviors or products start epidemics and others don’t? And what can we
do to deliberately start and control positive epidemics of our own?
ONE
The Three Rules of Epidemics
In the mid 1990s, the city of Baltimore was attacked by an epidemic of syphilis. In the space of a year, from 1995 to 1996, the number of children born with the disease increased by 500 percent. If you look at Baltimore’s syphilis rates on a graph, the line runs straight for years and then, when it hits 1995, rises almost at a right angle.
What caused Baltimore’s syphilis problem to tip? According to the Centers for Disease Control, the problem was crack cocaine. Crack is known to cause a dramatic increase in the kind of risky sexual behavior that leads to the spread of things like HIV and syphilis. It brings far more people into poor areas to buy drugs, which then increases the likelihood that they will take an infection home with them to their own neighborhood. It changes the patterns of social connections between neighborhoods. Crack, the CDC said, was the little push that the syphilis problem needed to turn into a raging epidemic.
John Zenilman of Johns Hopkins University in Baltimore, an expert on sexually transmitted diseases, has another explanation: the breakdown of medical services in the city’s poorest neighborhoods. “In 1990–91, we had thirty six thousand patient visits at the city’s sexually transmitted disease clinics,” Zenilman says. “Then the city decided to gradually cut back because of budgetary problems. The number of clinicians [medical personnel] went from seventeen to ten. The number of physicians went from three to essentially nobody. Patient visits dropped to twenty one thousand. There also was a similar drop in the amount of field outreach staff. There was a lot of politics—things that used to happen, like computer upgrades, didn’t happen. It was a worst case scenario of city bureaucracy not functioning. They would run out of drugs.”
When there were 36,000 patient visits a year in the STD clinics of Baltimore’s inner city, in other words, the disease was kept in equilibrium. At some point between 36,000 and 21,000 patient visits a year, according to Zenilman, the disease erupted. It began spilling out of the inner city, up the streets and highways that connect those neighborhoods to the rest of the city. Suddenly, people who might have been infectious for a week before getting treated were now going around infecting others for two or three or four weeks before they got cured. The breakdown in treatment made syphilis a much bigger issue than it had been before.
There is a third theory, which belongs to John Potterat, one of the country’s leading epidemiologists. His culprits are the physical changes in those years affecting East and West Baltimore, the heavily depressed neighborhoods on either side of Baltimore’s downtown, where the syphilis problem was centered. In the mid 1990s, he points out, the city of Baltimore embarked on a highly publicized policy of dynamiting the old 1960s style public housing high rises in East and West Baltimore. Two of the most publicized demolitions—Lexington Terrace in West Baltimore and Lafayette Courts in East Baltimore—were huge projects, housing hundreds of families, that served as centers for crime and infectious disease. At the same time, people began to move out of the old row houses in East and West Baltimore, as those began to deteriorate as well.
“It was absolutely striking,” Potterat says, of the first time he toured East and West Baltimore. “Fifty percent of the row houses were boarded up, and there was also a process where they destroyed the projects. What happened was a kind of hollowing out. This fueled the diaspora. For years syphilis had been confined to a specific region of Baltimore, within highly confined sociosexual networks. The housing dislocation process served to move these people to other parts of Baltimore, and they took their syphilis and other behaviors with them.”
What is interesting about these three explanations is that none of them is at all dramatic. The CDC thought that crack was the problem. But it wasn’t as if crack came to Baltimore for the first time in 1995. It had been there for years. What they were saying is that there was a subtle increase in the severity of the crack problem in the mid 1990s, and that change was enough to set off the syphilis epidemic. Zenilman, likewise, wasn’t saying that the STD clinics in Baltimore were shut down. They were simply scaled back, the number of clinicians cut from seventeen to ten. Nor was Potterat saying that all Baltimore was hollowed out. All it took, he said, was the demolition of a handful of housing projects and the abandonment of homes in key downtown neighborhoods to send syphilis over the top. It takes only the smallest of changes to shatter an epidemic’s equilibrium.
The second, and perhaps more interesting, fact about these explanations is that all of them are describing a very different way of tipping an epidemic. The CDC is talking about the overall context for the disease—how the introduction and growth of an addictive drug can so change the environment of a city that it can cause a disease to tip. Zenilman is talking about the disease itself. When the clinics were cut back, syphilis was given a second life. It had been an acute infection. It was now a chronic infection. It had become a lingering problem that stayed around for weeks. Potterat, for his part, was focused on the people who were carrying syphilis. Syphilis, he was saying, was a disease carried by a certain kind of person in Baltimore—a very poor, probably drug using, sexually active individual. If that kind of person was suddenly transported from his or her old neighborhood to a new one—to a new part of town, where syphilis had never been a problem before—the disease would have an opportunity to tip.
There is more than one way to tip an epidemic, in other words. Epidemics are a function of the people who transmit infectious agents, the infectious agent itself, and the environment in which the infectious agent is operating. And when an epidemic tips, when it is jolted out of equilibrium, it tips because something has happened, some change has occurred in one (or two or three) of those areas. These three agents of change I call the Law of the Few, the Stickiness Factor, and the Power of Context.
1.
When we say that a handful of East Village kids started the Hush Puppies epidemic, or that the scattering of the residents of a few housing projects was sufficient to start Baltimore’s syphilis epidemic, what we are really saying is that in a given process or system some people matter more than others. This is not, on the face of it, a particularly radical notion. Economists often talk about the 80/20 Principle, which is the idea that in any situation roughly 80 percent of the “work” will be done by 20 percent of the participants. In most societies, 20 percent of criminals commit 80 percent of crimes. Twenty percent of motorists cause 80 percent of all accidents. Twenty percent of beer drinkers drink 80 percent of all beer. When it comes to epidemics, though, this disproportionality becomes even more extreme: a tiny percentage of people do the majority of the work.
Potterat, for example, once did an analysis of a gonorrhea epidemic in Colorado Springs, Colorado, looking at everyone who came to a public health clinic for treatment of the disease over the space of six months. He found that about half of all the cases came, essentially, from four neighborhoods representing about 6 percent of the geographic area of the city. Half of those in that 6 percent, in turn, were socializing in the same six bars. Potterat then interviewed 768 people in that tiny subgroup and found that 600 of them either didn’t give gonorrhea to anyone else or gave it to only one other person. These people he called nontransmitters. The ones causing the epidemic to grow—the ones who were infecting two and three and four and five others with their disease—were the remaining 168. In other words, in all of the city of Colorado Springs—a town of well in excess of 100,000 people—the epidemic of gonorrhea tipped because of the activities of 168 people living in four small neighborhoods and basically frequenting the same six bars.
Who were those 168 people? They aren’t like you or me. They are people who go out every night, people who have vastly more sexual partners than the norm, people whose lives and behavior are well outside of the ordinary. In the mid 1990s, for example, in the pool halls and roller skating rinks of East St. Louis, Missouri, there was a man named Darnell “Boss Man” McGee. He was big—over
six feet—and charming, a talented skater, who wowed young girls with his exploits on the rink. His specialty was thirteen and fourteen year olds. He bought them jewelry, took them for rides in his Cadillac, got them high on crack, and had sex with them. Between 1995 and 1997, when he was shot dead by an unknown assailant, he slept with at least 100 women and—it turned out later—infected at least 30 of them with HIV.
In the same two year period, fifteen hundred miles away, near Buffalo, New York, another man—a kind of Boss Man clone—worked the distressed downtown streets of Jamestown. His name was Nushawn Williams, although he also went by the names “Face,” “Sly,” and “Shyteek.” Williams juggled dozens of girls, maintaining three or four different apartments around the city, and all the while supporting himself by smuggling drugs up from the Bronx. (As one epidemiologist familiar with the case told me flatly, “The man was a genius. If I could get away with what Williams did, I’d never have to work a day again in my life.”) Williams, like Boss Man, was a charmer. He would buy his girlfriends roses, let them braid his long hair, and host all night marijuana and malt liquor–fueled orgies at his apartments. “I slept with him three or four times in one night,” one of his partners remembered. “Me and him, we used to party together all the time....After Face had sex, his friends would do it too. One would walk out, the other would walk in.” Williams is now in jail. He is known to have infected at least sixteen of his former girlfriends with the AIDS virus. And most famously, in the book And the Band Played On Randy Shilts discusses at length the so called Patient Zero of AIDS, the French Canadian flight attendant Gaetan Dugas, who claimed to have 2,500 sexual partners all over North America, and who was linked to at least 40 of the earliest cases of AIDS in California and New York. These are the kinds of people who make epidemics of disease tip.
The Tipping Point Page 2
