Event data come in a variety of forms and coding schemes. The most widely cited sources are Azar's (1982) COPDAB (Conflict and Peace Data Bank) and McClelland's WEIS (World Events Interaction Survey). Both are comprehensive: they attempt to code all interactions by all states and some non-state actors during for a period of time.
In contrast, specialized event data sets such as Hermann's (1973) CREON (Comparative Research on the Events of Nations) and Leng's (1987) BCOW (Behavioral Correlates of War) focus on specific subsets of behavior, foreign policy and crises respectively. A variety of domestic and international event data collections, usually focusing on a limited set of actions such as uses of force, domestic violence, or changes of government, are embedded in other data sets such as Rummel's DON (Dimensionality of Nations), the World Handbook, and various Gurr data sets. In addition to the data sets in the public domain, event data have also been collected by governmental agencies such as Department of Defense and various intelligence agencies in the United States and private consulting firms such as CACI Inc. and Third Point Systems.
Figure 1 shows the actions that the United States directed towards the Soviet Union for the period 1948-1978 as measured by the Conflict and Peace Data Bank (COPDAB) event data set collected by the late Edward Azar (1980,1982). In the COPDAB coding scheme, negative numbers indicate conflictual behavior; positive numbers indicate cooperation. COPDAB is based on The New York Times and a variety of regional newspaper sources; the data cover the period 1948-1978. The COPDAB time series shows three general periods. The early Cold War (1948-1962) is characterized by uniformly negative relations, though these are more stable in the late 1950's than in the early 1950's. A partial "thaw" occurs in 1962-1970 following the Cuban Missile Crisis, with the relationship being neutral. Finally, the 1970-1978 period shows the rise and fall of the détente policy. Other event data sets covering the 1980s record the "new Cold War" of the early Reagan period followed by the improved relations that occur when Gorbachev comes to power in the USSR.