Page last updated at 13:48 GMT, Monday, 9 June 2008 14:48 UK

Why the oil price keeps rising

Iran-Iraq war Oil price crashGulf warAsian financial crisis 9/11Iraq warLebanon conflict $100 barrel Arab-Israeli war $139 barrelIranian revolution

Oil has hit a new high of $139 a barrel, only six months after hitting the $100 mark. The continued rise is partly due to a shortage in supply and continued demand from market investors convinced the price will keep on rising.

Chart how the price of oil has risen - and fallen - since 1970 against a background of key world events.

Israeli tanks
Israeli tank unit in the Golan Heights
Fighting between Arab and Israeli forces sent jitters through the Middle East.

Alarmed by Israeli successes, the Organisation of Petroleum Exporting Countries (Opec) orchestrated the Arab oil embargo, sending prices soaring by 400% in six months.

It was the first time oil had been used as a political weapon, putting pressure on the US which, in turn, persuaded Israel to accept UN mediation on the crisis.

Demonstrators holding posters of Ayatollah
Demonstrators support Ayatollah Khomeini

Months of turmoil in Iran led to the exile of the Shah and the declaration of an Islamic republic.

It also led to a reduction in oil production and, at one point, the flow of crude oil from Iran was almost halted. Nervousness about the stability of Iran brought together the other major Arab oil-producing states to ensure supply and increase prices.

Saddam Hussein
Saddam Hussein addresses his troops

Iran weakened by the revolution was invaded by Iraq in September 1980. By November, the combined oil production of the two countries was only one million barrels a day, 6.5m fewer barrels than the year before.

It meant a worldwide reduction in crude oil production of 10%. The combination of the Iranian revolution and the Iran-Iraq war caused crude oil prices to more than double from $14 in 1978 to $35 in 1981.

Higher oil prices led to a reduction in demand as consumers and industry looked at ways of becoming more energy-efficient.

The price rise also led to increased exploration for new sources of oil outside the traditional oil-producing regions.

Saudi Arabia suffered from the reduction in revenue, made worse by new Opec quotas which meant it had also been forced to reduce production.

It responded by increasing production in early 1986.

Crude oil prices plummeted below $10 per barrel - but the Saudi revenue remained about the same.

Tomcat landing
F14 Tomcat landing

The Iraqi invasion of Kuwait, partly prompted by the low price of oil, led to uncertainty about production and prices spiked.

Iraq wanted to gain control of the world's third largest oil producer to give it more control over the world market.

Following the Gulf war to liberate Kuwait, crude oil prices entered a period of steady decline, reaching their lowest level in 1994 for 21 years.

The rapid growth in Asian economies came to a halt leading to lower consumption of oil - just at a time when Opec had begun increasing production.

The combination sent prices plummeting, through to December 1998.

Manhattan skyline
9/11 attacks on World Trade Center

Oil prices suffered a downturn as Russian oil production increased, and the US economy went into decline.

Opec tried to stem the reduction by cutting production - but the terror attacks on 11 September sent oil prices plummeting again.

Prices were down by about 35% by the middle of November. Opec delayed cutting production again until early 2002, when prices began to move upwards once more.

Statue being pulled down
Saddam Hussein's statue is toppled

The American-led invasion of Iraq led to the loss of oil production in the Gulf state. In mid- 2002, there were over six million barrels per day of excess production capacity and by mid 2003, this had dropped to below two million.

It dropped still further in 2004-5. A million barrels per day is not enough spare capacity to cover for any sudden drop in production and it led to an increase in prices.

Israeli soldiers marching to Lebanon
After Israel launched attacks on Lebanon, oil prices reached a new high of $78 per barrel.

Although neither Israel nor Lebanon are oil producers, the conflict increased tension in the Middle East sending prices soaring.

Geopolitical tension in Kenya, Algeria and Pakistan, as well as the threat of US sanctions against Iran have played their part.

At the same time, there are fears of a cold winter in the US and Europe, and increased demand from China and India as well as the US.

The falling US dollar has also driven up oil prices as they have to gain to compensate for a slide in the currency.

Petrol price sign
Petrol prices soar as oil hits $135

Oil prices continued to rise after hitting $100 a barrel and crude reached a new record of $139 until 6 June 2008.

There seem to be a number of reasons for the increase; the supply of crude oil does not appear to have been keeping pace with demand as Asian economies continue to expand.

But the increase is probably also partly due to speculators investing in the market in the belief that prices will keep on going up - while oil producers have been slow to increase production.

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