From the mid-1980s to September 2003, the inflation-adjusted price of a barrel of crude oil on NYMEX was generally under US$25/barrel in 2008 dollars. During 2003, the price rose above $30, reached $60 by 11 August 2005, and peaked at $147.30 in July 2008. Commentators attributed these price increases to multiple factors, including Middle East tension, soaring demand from China, the falling value of the U.S. dollar, reports showing a decline in petroleum reserves, worries over peak oil, and financial speculation.

For a time, geopolitical events and natural disasters had strong short-term effects on oil prices, such as North Korean missile tests, the 2006 conflict between Israel and Lebanon, worries over Iranian nuclear plans in 2006, Hurricane Katrina, and various other factors. By 2008, such pressures appeared to have an insignificant impact on oil prices given the onset of the global recession. The recession caused demand for energy to shrink in late 2008, with oil prices collapsing from the July 2008 high of $147 to a December 2008 low of $32. However, it has been disputed that the laws of supply and demand of oil could have been responsible for an almost 80% drop in the oil price within a six-month period. Oil prices stabilized by August 2009 and generally remained in a broad trading range between $70 and $120 through November 2014, before returning to 2003 pre-crisis levels by early 2016, as US production increased dramatically. The United States went on to become the largest oil producer by 2018.

New inflation-adjusted peaks The price of crude oil in 2003 traded in a range between $20–$30/bbl. Between 2003 and July 2008, prices steadily rose, reaching $100/bbl in late 2007, coming close to the previous inflation-adjusted peak set in 1980. A steep rise in the price of oil in 2008 – also mirrored by other commodities – culminated in an all-time high of $147.27 during trading on 11 July 2008, more than a third above the previous inflation-adjusted high.

High oil prices and economic weakness contributed to a demand contraction in 2007–2008. In the United States, gasoline consumption declined by 0.4% in 2007, then fell by 0.5% in the first two months of 2008 alone. Record-setting oil prices in the first half of 2008 and economic weakness in the second half of the year prompted a /day contraction in US consumption of petroleum products, representing 5.8% of total US consumption, the largest annual decline since 1980 at the climax of the 1979 energy crisis.

Possible causes

Demand World crude oil demand grew an average of 1.76% per year from 1994 to 2006, with a high of 3.4% in 2003–2004. World demand for oil is projected to increase 37% over 2006 levels by 2030, according to the 2007 U.S. Energy Information Administration's (EIA) annual report. In 2007, the EIA expected demand to reach an ultimate high of , from 2006's , driven in large part by the transportation sector. A 2008 report from the International Energy Agency (IEA) predicted that although drops in petroleum demand due to high prices have been observed in developed countries and are expected to continue, a 3.7 percent rise in demand by 2013 is predicted in developing countries. This is projected to cause a net rise in global petroleum demand during that period.

Transportation consumes the largest proportion of energy, and has seen the largest growth in demand in recent decades. This growth has largely come from new demand for cars and other personal-use vehicles powered by internal combustion engines. This sector also has the highest consumption rates, accounting for approximately 55% of oil use worldwide as documented in the Hirsch report and 68.9% of the oil used in the United States in 2006. Cars and trucks are predicted to cause almost 75% of the increase in oil consumption by India and China between 2001 and 2025. In 2008, auto sales in China were expected to grow by as much as 15–20 percent, resulting in part from economic growth rates of over 10 percent for five years in a row.

Demand growth is highest in the developing world, but the United States is the world's largest consumer of petroleum. Between 1995 and 2005, US consumption grew from a day to a day, an increase of a day. China, by comparison, increased consumption from a day to a day, an increase of a day, in the same time frame. Per capita, annual consumption is by people in the US,20.7 Mbpd divided by the population of 304 million times 365 days/year in China,6.5 Mbpd divided by the population of 1,325 million people times 365 days/year (figures from the CIA Factbook ) and in India.2.45 Mbpd divided by the population of 1,136 million people times 365 days/year (figures from the CIA Factbook )

As countries develop, industry, rapid urbanization and higher living standards drive up energy use, most often of oil. Thriving economies such as China and India are quickly becoming large oil consumers.Oil price 'may hit $200 a barrel' , BBC News, 7 May 2008. China has seen oil consumption grow by 8% yearly since 2002, doubling from 1996–2006.

Although swift continued growth in China is often predicted, others predict that China's export-dominated economy will not continue such growth trends due to wage and price inflation and reduced demand from the US. India's oil imports are expected to more than triple from 2005 levels by 2020, rising to .

Another large factor on petroleum demand has been human population growth. Because world population grew faster than oil production, production per capita peaked in 1979 (preceded by a plateau during the period of 1973–1979). The world’s population in 2030 is expected to be double that of 1980.

Role of fuel subsidies State fuel subsidies shielded consumers in multiple nations from higher market prices, but a number of these subsidies were reduced or removed as the governmental cost rose.

In June 2008, AFP reported that:

In the same month, Reuters reported that:

The Economist reported: "Half of the world's population enjoys fuel subsidies. This estimate, from Morgan Stanley, implies that almost a quarter of the world's petrol is sold at less than the market price." U.S. Secretary of Energy Samuel Bodman stated that around of oil consumption (over a third of the global total) was subsidized.

Supply

An important contributor to the price increase was the slowdown in oil supply growth, which has been a general trend since oil production surpassed new discoveries in 1980. The likelihood that global oil production will decline at some point, leading to lower supply, is a long-term fundamental cause of rising prices. Although there is contention about the exact time at which global production will peak, a majority of industry participants acknowledge that the concept of a production peak is valid. However, some commentators argued that global warming awareness and new energy sources would limit demand before the effects of supply could, suggesting that reserve depletion would be a non-issue.

A large factor in the lower supply growth of petroleum has been that oil's historically high ratio of Energy Returned on Energy Invested is in significant decline. Petroleum is a limited resource, and the remaining accessible reserves are consumed more rapidly each year. Remaining reserves are increasingly difficult to extract and therefore more expensive. Eventually, reserves will only be economically feasible to extract at extremely high prices. Even if total oil supply does not decline, increasing numbers of experts believe the easily accessible sources of light sweet crude are almost exhausted and in the future the world will depend on more-expensive unconventional oil reserves and heavy crude oil, as well as renewable energy sources. It is thought by a number of people, including energy economists such as Matthew Simmons, that prices could continue to rise indefinitely until a new market equilibrium is reached at which point supply satisfies worldwide demand.

Timothy Kailing, in a 2008 Journal of Energy Security article, pointed out the difficulty of increasing production in mature petroleum regions, even with vastly increased investment in exploration and production. By looking at the historical response of production to variation in drilling effort, he claimed that very little increase of production could be attributed to increased drilling. This was due to a tight quantitative relationship of diminishing returns with increasing drilling effort: As drilling effort increased, the energy obtained per active drill rig was reduced according to a severely diminishing power law. This analysis suggested that even an enormous increase of drilling effort was unlikely to lead to significantly increased oil and gas production in a mature petroleum region like the United States.

A prominent example of investment in non-conventional sources is seen in the Canadian oil sands. They are a far less cost-efficient source of heavy, low-grade oil than conventional crude; but when oil trades above $60/bbl, the tar sands become attractive to exploration and production companies. While Canada's oil sands region is estimated to contain as much "heavy" oil as all the world's reserves of "conventional" oil, efforts to economically exploit these resources lag behind the increasing demand of recent years.

Until 2008, CERA (a consulting company wholly owned by energy consultants IHS Energy) did not believe this would be such an immediate problem. However, in an interview with The Wall Street Journal, Daniel Yergin, previously known for his quotes that the price of oil would soon return down to "normal", amended the company's position on 7 May 2008 to predict that oil would reach $150 during 2008, due to tightness of supply. This reversal of opinion was significant, as CERA, among other consultancies, provided price projections that were used by multiple official bodies to plan long-term strategy in respect of energy mix and price.

Other major energy organisations, such as the International Energy Agency (IEA), had already been much less optimistic in their assessments for some time. Interview with Fatih Birol. In 2008, the IEA drastically accelerated its prediction of production decline for existing oilfields, from 3.7% a year to 6.7% a year, based largely on better accounting methods, including actual research of individual oil field production throughout the world.George Monbiot asks Fatih Birol, chief economist of IEA, when will the oil run out? , The Guardian,

Terrorist and insurgent groups have increasingly targeted oil and gas installations, and succeeded in stopping a substantial volume of exports during the 2003–2008 height of the American occupation of Iraq. Such attacks are sometimes perpetrated by militias in regions where oil wealth has produced few tangible benefits for the local citizenry, as is the case in the Niger Delta.

A number of factors have resulted in possible and/or actual concerns about the reduced supply of oil. The post-9/11 war on terror, labor strikes, hurricane threats to oil platforms, fires and terrorist threats at refineries, and other short-lived problems are not solely responsible for the higher prices. Such problems do push prices higher temporarily, but have not historically been fundamental to long-term price increases.

Investment/speculation demand Investment demand for oil occurs when investors purchase futures contracts to buy a commodity at a set price for future delivery. "Speculators are not buying any actual crude. ... When [the] contracts mature, they either settle them with a cash payment or sell them on to genuine consumers."