Summary

Gladwell opens his book with a dictionary definition of the word "outlier." It is "something that is situated away from or classed differently from a main or related body," and also "a statistical observation that is markedly different in value from others of the sample." His first example of an outlier is the town of Roseto, Pennsylvania in the first half of the 20th century.

Roseto is founded by Italian immigrants in the late 19th century. Most of the early residents are from a town in Italy, also called Roseto, after which the Pennsylvania town is named. The town grows up around the local slate quarry business and the residents reconstruct an American version of their Italian homeland.

What makes Roseto, Pennsylvania an "outlier" is that the residents are remarkably healthy when compared to other Americans. This fact comes to light...