Mesolevel networks and the diffusion of social movements: The case of the Swedish Social Democratic Party

In analyzing the spatial diffusion of the Swedish Social Democratic Party, this article introduces the notion of a mesolevel network. A mesolevel netw ork is a social network that differs in three important respects from inter personal microlevel networks directly linking prior and potential adopters of a practice to one another: (1) it is generated by a different causal pro cess than the microlevel network; (2) it tends to be much sparser than the microlevel network; and (3) the typical edge of a mesolevel network bridges much longer sociometric and geographic distances than the typical edge of a microlevel network. These types of mesolevel networks are important becau se they can dramatically influence the speed at which a contagious practice will diffuse. The mesolevel network focused upon in this article is the ne twork that emerged out of the travel routes of political agitators affiliat ed with the Social Democratic Party. Computational modeling shows that the diffusion of the Social Democratic Party is likely to have been considerabl y influenced by the structure of this network. Empirical analyses of the fo unding of party organizations during the period 1894-1911 support these the oretical predictions and suggest that this mesolevel network was of conside rable importance for the diffusion of the Swedish Social Democratic Party.