This clique played a central role in the diffusion of modern math among Pittsburg’s schools. Once the clique members (especially the three main opinion leaders show decided to use the innovation in 1959 and 1960) adopted, the rate of adoption of modern math began to climb rapidly. Figure 8-1 shows that there was only one adopter in 1958 (the innovator), five by the end of 1959, fifteen by 1960, twenty-seven by 1961, thirty-five by 1962, and all thirty-eight by the end of 1963. The rapid spurt in 1959, 1960, and 1961 appeared to occur as a direct result of the opinion leaders’ adoption