Is war the result of a social or economic effect?

If you had to choose social or economic roots of war, economic probably wins out.  Most wars are fought for some economic benefit or to offset a perceived threat to economic advantage.  This is especially true of American involvement in warfare.  Dating back to World War I, when the United States entered on the side of the Allies to protect its investments, the United States has been actively involved in warfare to protect economic interests.  If you look at the history of American intervention in World War I, the proxy wars of Vietnam and Korea, and involvement in the Middle East, the United States has typically used its military to secure economic objectives. 

In the history of the world outside of the United States, wars were often times fought over resources in an effort to achieve an economic benefit.