(7) The first stream is the problem stream. For policy change to take place, policy actors must first recognize that there is an existing problem. The most obvious way for a condition to become a problem is through a "focusing event." Focusing events are highly public events that call attention to a particular issue. For example, the disaster at Three Mile lsland was a focusing event for nuclear power, ultimately shifting the focus away from energy efficiency to health and safety concerns. "Indicators" such as regularly conducted surveys or published reports can also raise awareness of an existing condition, but focusing events tend to be more effective. The media also plays an important role in shaping the saliency of a particular issue. Again, as other agenda-setting scholars have suggested, policy definition and policy image are crucial to moving a condition onto the government agenda(see Stone 2002).