Bonding social capital is inward looking, reinforcing exclusive identities and homogeneous groups (22). It is marked by close ties, such as those found in ethnic organizations. While important for people, Putnam considers this not only the less socially important form of capital but also one that can potentially have negative effects, such as sectarianism and corruption.

Bridging social capital is inclusive and outward looking, with diverse groups of people (22). It creates weaker ties in the form of acquaintances versus friends. However, Putnam deems it the more important form of social capital, as it creates broader identities and encourages reciprocity. The two types of social capital are not mutually exclusive but operate in overlapping dimensions.

A correlation exists when two variables fluctuate in relation to one another. A correlation is positive if the two variables move in the same direction and negative if one variable decreases while the other increases. Putnam uses correlational analysis to explain the decline in social capital and is careful to denote that correlation is different from causation.