A structured overview of 50 years of small-world research

This paper offers a structured overview of 50 years of small-world research. Initially formulated by Pool and Kochen in the mid-1950s, the small-world concept can be divided into six research foci, based on three dimensions (structural, process-related, psychological), and two process-related themes (diffusion, search). Building on this analytical distinction, the article provides a historical summary of the different phases of research on the small-world problem, and summarizes the empirical and theoretical progress on different facets of the small-world phenomenon. The paper concludes with a brief assessment of accomplishments and open questions, suggesting some possible future research areas.