The price of crude oil, the interplay between supply and demand, and taxes and inflation all influence the price of gasoline, but the historical gas price doesn't predict future trends. The recent drop in oil prices is a response to the boom of shale oil production in the United States.
As the United States has produced significant yields in shale oil, the Organization of Petroleum Exporting Countries, or OPEC, has kept its production levels high as well. It hopes that the drop in oil prices makes shale oil production unprofitable for American companies. Historically the price of gasoline was pushed upwards by factors such as conflict in the Middle East and increases in demand for gasoline worldwide.