Legislative Member Organizations as Social Networks in the United States and the European Union


Legislative member organizations (LMOs) are voluntary organizations within lawmaking bodies that are made up of members who share a common interest in a particular political issue or theme. Examples include the Animal Welfare Intergroup, the Trade Union Intergroup, and the Anti-Racism & Diversity Intergroup (in the European Parliament) or the Black Caucus, the Caucus for Women’s Issues, the Mining Caucus, and the Rural Health Care Coalition (in the U.S. Congress).

We propose that LMOs allow legislators to establish internal information networks based on policy priorities that transcend the boundaries imposed by partisanship, opposing ideology, and committee jurisdictions. Critically, these networks are mainly comprised of weak, bridging ties between legislators and their offices (Granovetter 1973, 1974). Information flows more efficiently through these networks because much of the information circulating in a social network composed of strong ties tends to be redundant, due to the frequent interactions between all network members. LMO ties thus transcend closely-tied social circles that would be isolated from each other in their absence, because they span structural holes in the legislative network by cutting across party and committee lines (Burt 1992, 2000, 2004). Hence, LMO ties help to efficiently diffuse socially distant ideas and information that are relevant to legislators’ policy choices, which helps mitigate the informational collective action dilemma prevalent in legislative politics, where a great demand for political and policy information is met with an insufficient supply.

One of the key characteristics of LMOs that allow them to play this role is their voluntary nature—legislators can join (or depart) at will. This reality entails that LMO networks are endogenous from the point of view of individual legislators, since ties are formed as a result of their voluntary participation in one or more LMOs. It also means that the issue scope of LMOs is open, because a group of legislators can set up LMOs on any issue they consider to be a policy priority, and that the set of participants is ideologically heterogeneous, because legislators join groups based on shared substantive interests rather than shared preferences. Finally, the voluntary nature of LMOs makes participation cheap, for two reasons. First, voluntary membership means that most LMO ties are weak ties, as participation in LMOs for most legislators is too limited to provide for the establishment of strong ones. Weak ties are cheap, however, because they do not require much effort when it comes to creating and maintaining them. Second, LMOs are low-cost for most participants because voluntary participation means that members are invited to free-ride on the informational benefits LMOs offer. The costs associated with establishing and running LMOs are borne either by legislators who have a strong enough personal stake in the LMO’s issue to voluntarily expend some of their limited resources, and/or by outside advocacy organizations that support an LMO’s cause.

The relationships between LMOs and outside advocates are quite extensive, and we highlight two aspects of the involvement of outsiders in LMO systems: the privileged relationships they maintain with LMOs and their leaders, which consist of outsiders providing legislative subsidies to lawmakers who share their policy priorities, and the nature of information exchange between insiders and outsiders. LMO ties between insiders and outsiders encourage the flow of high-utility information into the legislature, or information that is research-based, reliable, and presented in an easily-digestible format. The LMO network inside the legislature, in turn, efficiently diffuses this information and allows lawmakers to make better policy choices.


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  • Burt, Ronald S. “Structural Holes and Good Ideas.” American Journal of Sociology 110(2) (2004): 349-99.
  • Granovetter, Mark. “The Strength of Weak Ties.” American Journal of Sociology 78 (1973): 1360-80.
  • Granovetter, Mark. Getting a Job. Cambridge, MA: Harvard University Press, 1974.