With the music industry as a guide, economists have developed a time-tested model of superstars that has repercussions for the wider economy. As I explain in Chapter 4, two essential features of a market are necessary for a sector to be dominated by a small number of stars. First, there must be scale economies, meaning that someone can apply his or her talents to a large audience with little additional cost per audience member. Second, the players need to be imperfect substitutes, meaning that their work is differentiated and unique. Both elements are present in music. Every successful singer, band, and orchestra has a unique sound. And recorded music can reach billions of listeners at little additional cost once a recording is made. By contrast, in medicine, for example, some surgeons are much better than others, but they are limited by the number of, say, hip replacements they can perform in a day. The top surgeons do well, but they do not do nearly as well compared to lesser surgeons as top musicians do compared to every other recording artist.