Crude oil prices have risen by around 30% this year.
The reasons for this are diverse, hinging on the age-old conundrum of supply and demand.
Developing economies are responsible for a leap in demand for oil to drive their growth. China's oil use alone has risen by 20% year on year.
Stocks are also low, because oil companies have made significant savings in recent years by trying to operate more efficiently. That means they stock less oil, but this in turn means that the industry can't react quickly to surges in demand or disruptions in supply.
This situation is not helped by OPEC, a cartel of oil-producing nations, acting more aggressively to keep prices high, as well as civil unrest in the Middle East, Nigeria and Venezuela that has disrupted supplies.
Speculators are also driving prices up as they buy up stocks of oil, anticipating making money from price rises. With oil stocks so low, their buying oil and holding it as an investment inevitably means that prices are driven up as supply is squeezed further.