Constitutional rules define the most general context of the games agents are allowed to play. Second, it is useful to point out the different levels of rules that can be relevant in institutional analysis (see Ostrom 1990, Chap. Thus, formal institutional constraints are often supplemented by informal rules and vice versa. Committee power in democratic political bodies is determined to a large extent by informal norms that foster vote exchange (logrolling) (Coleman 1973, Shepsle and Weingast 1987) and only to a minor degree depends on formal rules. However, it is important to notice that formal rules are embedded in informal norms. There are also complex formal institutions regulating political committees in political systems and collective decisions in large capitalist firms. Among the most elaborate formal institutions in modern societies one should mention the law. Formal institutions are generally created and arranged by agents who are able to rely on third parties for monitoring and enforcement. Though conventions are defined as self-enforcing, they often become codified in formal rules (e.g., time standards or traffic rules).

Other informal institutions are conventions. These institutions include, for example, social norms of self-help among residents in rural communities (see Ellickson 1991). Informal institutions do not rely on an external authority's monitoring and policing of the participants' behavior. Furthermore, there are formal and informal institutions. The prisoner's dilemma and public good situations are cases in point. Social dilemmas are situations where interdependent agents are faced with choices for which individual rationality does not yield a socially optimal outcome. For example, it can be argued that social institutions typically regulate social dilemmas. In contrast to personal rules, social rules affect social interactions, that is, recurrent situations of social interdependence. But they are not social institutions in the proper sense. Personal rules may be motivated by individuals' long-term interests to achieve self-control. Some of these rules may be interpreted as attempts of individuals to bind themselves. These personal rules (e.g., the rule to go early to bed every night) resemble individual habits and individual routines. There are rules that regulate the personal life of human agents. First, adopting the intuitive meaning of institutions as rules or constraints of behavior, it is useful to make the following distinctions. There are many different kinds of institutions.

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