There are several factors behind the relationship between natural resources and armed conflicts. Resource wealth may increase the vulnerability of countries to conflicts by undermining the quality of governance and economic performance (the "resource curse" argument). Secondly, conflicts can occur over the control and exploitation of resources and the allocation of their revenues (the "resource war" argument). Thirdly, access to resource revenues by belligerents can prolong conflicts (the "conflict resource" argument). A 2018 study in the "Journal of Conflict Resolution" found that rebels were particularly likely to be able to prolong their participation in civil wars when they had access to natural resources that they could smuggle.