Goat, what has been the main cause of gas prices tripling in the last 6 years?
Three things:
1) The declining value of the dollar. Oil is a worldwide commodity traded in US dollars.
2) Speculation. As the equities markets tanked, more investment money was diverted into commodities, particularly oil.
3) Rapidly increasing worldwide demand. The Chinese want to live like us. They need oil to do it. Demand goes up, price goes up.