According to Robert Cialdini
People want to be with the crowd. It tells them something not only about what’s appropriate, but what’s possible for them.
If we send people in San Diego a message saying the majority of your neighbors are conserving energy on a daily basis, that has more effect than telling them to do it for the environment or to be socially responsible citizens or to save money. If your neighbors are doing it, it means it’s feasible. It’s practicable. You can do it—people like you.
It was very important that we say “people in your neighborhood.” If we said “the majority of Americans,” that wasn’t effective. If we said “the majority of Californians,” that was more effective. If we said “the majority of San Diegans,” that was more effective. But the most effective was “the majority of your neighbors.” That’s how you decide what’s possible for you: what people in your circumstance are able to do.