In trying to ascertain the number of IGO's which exist in the global system at any given point in time, we had to develop classification criteria and coding rules which answered the following questions. First, how do we distinguish IGO's from other pacts, protocols, arrangements, and agreements undertaken between governments? Second, exactly how do we distinguish IGO's from NGO'S, given the wide spatial and temporal variations in the boundary between the public and the private sectors? Third, at which point in the often lengthy genesis of an organization shall it be deemed to come into existence, and—what is usually more difficult to answer—when shall it be deemed to have ceased to exist? Fourth, how shall we decide when two IGO's shall be said to be independent of one another, given the modern tendency toward complex administrative connections between them?

The criteria for the inclusion of IGO's are as follows. First, the organization must consist of at least two qualified members of the international system, as defined in the next section. It may be objected, of course, that bilateral organizations should not be included on the grounds that they are not "really" IGO's as we usually conceive of them because they result from "contractual" rather than "lawmaking" treaties. There are two points two be made here. One, this objection is met by us in that mere treaties or pacts are excluded by other criteria; we only urge that an organization's bilateral character cannot of itself be grounds for exclusion.[The requirement that there be more than two participating nations before an organization be termed "international" is, apparently, a well-established definitional convention. Some have pointed out, however, that there is little empirical evidence to support it; see Adrea Rosenberg, International Associations, Vol. 19, No. 11.] Further, such exclusion would not only leave out such important organizations as the North American Air Defense Command (NORAD) but would also force us to drop such multilateral organizations as the Rhine River Commission when historical circumstances temporarily reduced their membership to two.[In this case, Baden and Wurtemburg ceased to be distinct members upon their absorption into Germany, and France lost her riparian territory in the Franco-Prussian war, leaving only the Netherlands and Germany as members between 1871 and 1918.]

Organizations must meet two additional criteria to qualify. One, the organizations must hold more or less regular plenary sessions at intervals not greater than once a decade. As a matter of fact, many writers have cited the regular meetings of IGO'S as one of the most crucial innovations of multilateral diplomacy.[For a comprehensive list of international plenary meetings during this period see International Congresses, 1686 to 1899 (Brussels: Union of International Associations, 1960) and International Congresses 1900-1919 (Brussels: Union of International Associations, 1964)]  This requirement of one meeting every ten years may seem lax, but we have found more stringent requirements inappropriate for the somewhat less hurried age prior to World War 1. The second additional requirement is a permanent secretariat and some sort of permanent headquarters arrangement. This condition is not particularly strict and does not require that the secretariat be "international" in the UN sense. Many international unions have their secretariats supplied by a single member, and not infrequently these are housed within a single national administration; one of the earliest examples is the Universal Postal Union. [Clyde Eagleton, International Government, (3rd edition; New York: Ronald Press, 1957) pp. 178, 187-189.] An organization also qualifies even if its secretariat personnel are supplied by various members on a rotating basis (as was the case with the International Association of Railway Congresses) or if they are provided by—but not identical with—the secretariat of another organization, a situation which often characterizes the relationship between the large specialized agencies and small organizations in proximate functional domains. The crucial distinction here is between ad hoc conferences or series of conferences whose staffs do not function between meetings and true organizations (even if labeled conferences or agreements) possessing secretariats which perform ongoing tasks.

Originally we contemplated adding the further requirement that the organization possess some provision for a regular budget, but we found that 1) this would be redundant in that a permanent secretariat would scarcely be possible without such arrangements and 2) information on budgetary arrangemens was almost impossible to come by in many cases. In those few cases in which information on the existence of an organized secretariat was missing or confusing but the existence of regular budgetary provisions could be definitely established, such budgetary provisions were deemed to have satisfied the secretariat requirement.

The second set of rules deals with the matter of separating IGO's from NGO's—in other words, determining whether it is governments that are the active participants. The difficulty is that there exist "mixed" organizations, some of whose delegations are appointed by governmental agencies or ministries and some by private bodies such as corporations. This state of affairs reflects the fact that in some areas, such as communications and banking, nations differ widely with respect to the degree of control exercised by the public authority. Following Eagleton, we concluded that it would be unreasonable to exclude organizations simply because a number of their members were not national states. Instead we adopted the criterion employed by the UN Economic and Social Council (ECOSOC): whether or not the organization was created by a formal instrument of agreement between the governments of national states. Eagleton, pp. 178-181; and ECOSOC Document E/INF/23, April 30, 1948, p. 16.]

A third set of criteria serves to set the dates marking the birth, death, and occasional resurrect-ion of each organization. In general, we count an organization as established on the opening date of the first plenary session, which is usually the organizing meeting. This is a more realistic indication of organizational birth than the date specified in the founding instrument, in as- much as the secretariat of most new organizations begins to 'function at or shortly after the organizing meetings and continues on a "provisional" basis while awaiting full ratification of its charter. Of course, given the complex gestation of many organizations, it is sometimes difficult to determine which of several meetings marks an IGO's operational beginning. In case of doubt we have used the meeting which resulted in the creation of a permanent secretariat as our date of establishment.

An organization ceases to exist in either of two circumstances. One is the lapse of ten years without a plenary meeting, in which case the date of termination is that of the closing of its last plenary conference. The second refers to circumstances in which one organization is formally replaced or succeeded by another. In this case, the first organization is deemed to cease on the founding date of the successor. These criteria are based on the active, rather than the legal, life of IGO'S. For one thing, the exact dates marking the beginning and end of an organization's legal existence are not always easy to determine, given the often prolonged interval between the signing and the ratification of the multilateral instruments which govern the process. [The theoretical and practical implications of this lag are discussed in Francis 0. Wilcox, The Ratification of International Conventions (London: Allen and Unwin, 1935).]   Moreover, it is obvious that in many cases the two life-spans will not corrtspond. On the one

Our final set of criteria is designed to determine when two IGO's are to be classified as independent of one another. Ambiguities are rare in the nineteenth century, but in recent decades IGO's have tended to form liaison associations among themselves (such as the Inter-American Committee for Agricultural Development) and to unite in families (such as the present UN com- plex). Our coding rules are as follows. First, an association or confederation of IGO's does not count as an additional IGO. Second, an IGO is independent only if two conditions are satisfied: 1) its membership is not selected wholly or in part by another IGO, ruling out, for example, the Economic and Social Council of the UN; and 2) the organization is serviced by administratively distinct secretariat personnel who function under the authority of the organizational plenum. This requirement excludes organizations which are merely subordinate or regional offices of a parent organization (for example, the International Poplar Commission under FAO) as well as those which are merely treaties or agreements administered by -the secretariat of another organization, such as the various "special unions" of the International Union for the Protection of Industrial Property. Included are organizations which, while owing their original existence, their personnel, and perhaps even their budget to the actions of a parent organization, exercise autonomous jurisdiction over their own secretariat. Finally, there arises occasionally an overlap problem of an- other sort: when two separate IGO's claim jurisdiction over the same domain, as do the Commission européenne du regime du Danube with headquarters in Rome and the (functioning) Danube Commission with headquarters in Budapest. In these cases only the organization with evident de facto control over the relevant domain is counted.

Having identified the qualifying organizations, the next step is to ascertain which nations constituted the membership of each during each of the 30 periods under study. This is obviously a two-phase operation, with identification of nation membership in the total international system an essential prerequisite to identification of each organization's membership. Fortunately, phase one has already been completed and needs merely to be summarized here. [For a detailed list of the entities qualifying as states members of the international system and an exposition of the coding rules governing their selection, see J. David Singer and Melvin Small, "The Composition and Status Ordering of the International System: 1815-1940," World Politics, January 1966 (Vol. 18, NO. 2), pp. 236-282; and Bruce M. Russett, J. David Singer, and Melvin Small, "National Political Units in the Twentieth Century: A Standardized List," American Political Science Review , September 1968 (Vol. 62, No. 3), pp. 932-951.] In general, a national political entity, to qualify for system membership, must have the standard attributes of national sovereignty plus a minimum population of 5oo,ooo. In addition, it must have the diplomatic recognition of both the United Kingdom and France (the so-called "legitimizers") up through World War I, along with missions at or above the chargé ' d'affaires rank from each. For the post-Versailles period, however, we dropped -the population requirement and demanded either ;the above recognition from any two major powers or membership in the League of Nations or the UN. These inclusion-exclusion criteria (with some ad hoc exceptions) produce a system population which ranges from 23 in 1815 to 122 in 1964, with the upward secular trend broken only by the Italian and German unifications and by the territorial occupations and realignments of the two world wars. We also distinguish, from 1815 to 1919, between "central system" nations and those of a more peripheral nature in order to reduce the statistical "noise" which the letter might generate and to permit focusing on those nations which are most closely associated with each other largely through the traditional European State system. However, we assume (but hope eventually to confirm) that the total system had become sufficiently interdependent after World War I to no longer justify so sharp a distinction between its members.

Once a nation satisfies the criteria for membership in the system as a whole, it is necessary to identify those which qualify it for membership in any given IGO. We employ three criteria. First, a nation must send working delegations to the plenary sessions of the organization, and these must have full voting rights, although of course a weighted voting system will not exclude any nation. [A few modern organizations admit "associate members," i.e., nations which have limited agreements with the organization, enabling them to participate in some of its activities without voting rights. The best-known example is the EEC which has special arrangements with Greece, Turkey, and a number of African states. For a detailed treatment of voting procedures see Wellington Koo, Jr., Voting Procedures in International Political Organizations (New York: Columbia University Press, 1947).]   As might be surmised from the earlier discussion, these delegations need not always be accredited by the governments of the nations concerned. Second, if a nation ceases to send full voting delegates to two meetings in a row, we deem it to have lost its membership and backdate its departure from its first absence. This rule applies even when the organization, the member concerned, or both, do not consider membership to have been terminated. On the other hand, we do not take account of boycotts, walkouts, suspensions, or expulsions unless they last longer than two complete plenary sessions. Our purpose here is to avoid a legalistic interpretation of membership, considering it rather in terms of actual participation in the organization's plenary and other activities. Finally, IGO's will frequently include territorial entities which are not state members of the international system, such as colonies, protectorates, provinces, or other subnational territorial units. If the metropolitan authority controlling these territories does not itself meet our other membership criteria, but the territory does, then we count the metropole as belonging indirectly, via its possession, since in one fashion or another it presumably has control over the possession's delegations If however the mother country is a member, the membership of its possession does not count as an additional one."