Voters remove elected official through early election.
By roughly 6000 to 8000 years ago, agriculture was well under way in several regions including Ancient Egypt, around the Nile River; the Indus Valley civilization; Mesopotamia, between the Tigris and Euphrates rivers; and Ancient China, along the Yellow and Yangtze rivers.
I'm not sure exactly what unit you're referring to, but three of the main factors that affect oil prices today would be natural disasters, futures trading, and global demand.
