Betweenness Centrality
the most valuable person in a network isn't the most popular - it's the one everyone has to go through
Grounded in the research on Wikipedia: Betweenness centrality; Linton Freeman (1977)
the setup
Betweenness centrality measures how often you sit on the shortest path between two other people. Not how many friends you have - how many connections route THROUGH you. Picture every pair in a network trying to reach each other by the fewest hops. The more of those paths pass over your shoulder, the higher your betweenness. You're not the popular one. You're the toll booth.
the science
Sociologist Linton Freeman formalized it in 1977 ("A Set of Measures of Centrality Based on Betweenness"), building on Bavelas's 1948 work on communication in small groups. It's a hard graph-theory metric, not vibes: count the shortest paths between every pair, then count how many run through you. High score means you bridge people who otherwise couldn't reach each other directly. Real math, decades of network research behind it.