Lack of diversity makes a group more susceptible to an epidemic.

Diversity is mentioned throughout the book in connection with population ratios as well as monocultures, where there is an entire lack of diversity. While discussing the Magic Third in Chapter Four, Gladwell describes how ratios of minorities affect a group. The community in Palo Alto where the neighborhood by design was one-third Black, one-third white, and one-third Asian also required that any two neighbors were of different ethnicities. The community had friendships and support throughout, not just within the specific groups, while most neighborhoods in the United States remained segregated. The intentional diversity structure removed the risk of a monoculture, and the members of the community thrived and became more accepting of different ethnicities and cultures.

The example of Poplar Grove demonstrates the risk of monocultures. Much as the cheetahs’ lack of genetic diversity made them more susceptible to disease, Poplar Grove’s lack of cultural diversity made it susceptible to an epidemic of suicide. Even though the school had different cultural groups of kids, they were all quite similar, since the school operated on a culture of intense academic pressure. The monoculture kept the students from expressing themselves and experimenting with autonomy. Where biodiversity makes an ecosystem or species more robust, having diversity within communities makes them more resilient (and ultimately less susceptible to epidemics). Since the parents were unwilling to change the culture, the epidemic continued for more than a decade.

Overstories can be influential even when they are subtle.

Throughout the book, Gladwell references the “overstories” that affect a specific area. In forestry science, the overstory is the leafy canopy that casts a shadow over everything below it. Down at the level of the forest floor, the shadow determines local conditions even if one does not look up to see all of the details of the canopy. People might not understand all of the elements of an overstory or how it came to be, but it still influences culture and behavior.

When describing Paul E. Madden’s efforts to track opioid prescriptions at the end of the book, Gladwell describes how a few states adopted and maintained the triplicate system. The system did enable the government to keep an eye on opioid prescriptions and prosecute doctors who were being negligent or corrupt, but it also changed how doctors felt about prescribing opioids. The doctors prescribed far fewer overall, even though they could have prescribed more without getting into trouble. It wasn’t just a safety measure; it changed the way the doctors viewed prescribing opioids. When Purdue Pharma’s sales reps went to push for more OxyContin prescriptions across the nation, they found that many of the doctors were less inclined, and not just because the paperwork was more complicated. The overstory of Madden’s efforts to document the prescriptions changed how everyone thought about opioids.

Skewed proportions in a group result in different behavior and perceptions of people within the group.

Group diversity is important for several reasons (see the first Main Idea, above), and not just because the ratio of people in a group determines when and whether that group tips. The ratio of individuals in a group changes how the group behaves and how the members of the group behave toward and around one another. One example Gladwell discusses is the inclusion of women on corporate boards. Once the number of women reaches a third (or more) of the total members, the women (and their ideas) are viewed as part of the whole, not as a minority perspective.

A single woman on a corporate board (or part of any small team responsible for making decisions) will usually have a difficult time. She will be perceived as the female member of the group and will not be perceived for who she actually is. Two women together have a somewhat easier time, but Gladwell found that three was the tipping point within the group. It was also the Magic Third, since most corporate boards are made up of approximately nine members. Once there were more than two women, the male group members shifted to treating them as individuals instead of as a representative of their gender. The differences between the women also demonstrated that they were unique, thinking individuals and not just a token representation. This group dynamic applies in most situations. Gladwell also supplies the example of minority students in a mostly white classroom. Once there are more than a few minority students, they can behave and act more as individuals.

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