Another graph from The Center for Systemic Peace:
The dashed line represents the dissolution of the Soviet Union in 1991.
From their explanation:
Ethnic wars, which had previously paralleled the trend of revolutionary war, continue to rise through the late 1980s and early 1990s as separatists and other political entrepreneurs attempt to take advantage of the vast changes in political arrangements that accompanied the transformation of the post-Cold War world system. Ethnic wars stand out like a “sore thumb” in the 1990s’ security environment. Also, notice that the long-term trend in ethnic warfare increases relatively smoothly as compared to the other warfare trends. As the goals of social identity conflicts are suffused with non-negotiable identity issues, these conflicts tend to persist and, so, are less susceptible to settlement or resolution by warfare. Thus, ethnic warfare trends are less ammenable to periodic fluctuation.
