# Brokers, bridges and structural holes

> A broker links groups that would otherwise be apart. Structural holes, weak ties, and cut points (the people whose removal splits a network), with an example.

Source: https://netgraf.isik.co/learn/brokers-and-bridges
Updated: 2026-09-24

A broker is a person who links people or groups that would otherwise be apart. The gap they span is a structural hole. When removing one person would actually split the network in two, that person is a cut point, or articulation point, and the network depends on them entirely.

## Structural holes and weak ties

Ronald Burt's theory of structural holes (1992) argues that people who bridge disconnected groups get earlier, more varied information and can play the groups against each other, which is why brokers are paid, promoted and listened to out of proportion to their number of ties. It builds on Mark Granovetter's "strength of weak ties" (1973): new jobs and ideas tend to arrive through acquaintances, because close friends already know what you know.

## Cut points

[Betweenness centrality](https://netgraf.isik.co/learn/betweenness-centrality) measures how much of the traffic a person carries. A cut point is the stronger condition: there is no other route at all. Remove a cut point and some people can no longer reach others. Hopcroft and Tarjan's 1973 algorithm finds every cut point in one pass over the network.

In the [Florentine families](https://netgraf.isik.co/m/florentine-families) the Medici are a cut point: some families reach the rest of the elite only through a Medici marriage. That dependence, not their wealth, is the structural story of their rise.

## In Netgraf

Size the map by **Holding it together** (betweenness) to see the brokers, and check the Insights panel's **How it breaks up** card for islands and people with no ties. The worked example below lists this map's cut points, computed live.

## Questions

### What is the difference between a bridge and a broker?

In graph theory a bridge is a tie whose removal disconnects the network, and a cut point is the equivalent person. Broker is the social term for anyone who connects otherwise separate people, whether or not they are the only route.

### Is being a broker good?

For the broker it usually brings information and leverage. For the network it is a risk: if the broker leaves, is overloaded or filters what passes, the groups they link lose contact. Organisations often add redundant ties on purpose.

## Example maps

- https://netgraf.isik.co/m/florentine-families
- https://netgraf.isik.co/m/krackhardt-kite

## References

- Burt, R. S. (1992). Structural Holes: The Social Structure of Competition. Harvard University Press.
- Granovetter, M. S. (1973). The strength of weak ties. American Journal of Sociology, 78(6), 1360-1380. https://doi.org/10.1086/225469
- Hopcroft, J., & Tarjan, R. (1973). Algorithm 447: Efficient algorithms for graph manipulation. Communications of the ACM, 16(6), 372-378. https://doi.org/10.1145/362248.362272
- Padgett, J. F., & Ansell, C. K. (1993). Robust action and the rise of the Medici, 1400-1434. American Journal of Sociology, 98(6), 1259-1319. https://doi.org/10.1086/230190