|Articles in this series:|
|Mitigation of peak oil|
|Hubbert peak theory|
As first expressed in Hubbert peak theory, peak oil is the point or timeframe at which the maximum global petroleum production rate is reached. After this timeframe, the rate of production will enter terminal decline. According to the Hubbert model, the production rate will follow a roughly symmetrical bell-shaped curve. This does not mean oil will suddenly "run out", but the supply of cheap conventional oil will drop and prices will rise, perhaps dramatically.
Some observers such as Kenneth S. Deffeyes and Matthew Simmons believe that because of the high dependence of most modern industrial transport, agricultural and industrial systems on inexpensive oil, the post-peak production decline and possible severe increases in the price of oil will have negative implications for the global economy. Predictions as to what exactly these negative effects will be vary greatly. More optimistic outlooks, delaying the peak of production to the 2020s or 2030s and assuming major investments in alternatives occur before the crisis, show the price at first escalates and then retreats as other types of fuel sources are used as transport fuels and fuel substitution in general occurs. More pessimistic predictions which operate on the thesis that the peak will occur shortly or has already occurred predict a global depression and even the collapse of industrial global civilization as the various feedback mechanisms of the global market cause a disastrous chain reaction. The shortfall will cause demand destruction which may be mitigated with planned conservation measures and using alternatives if implemented 20 years before the peak.. If political and economic change only occurs in reaction to high prices and shortages, then the degree of economic damage to importing countries will largely depend on how rapidly oil imports decline post-peak. The Export Land Model suggests that the amount of oil available internationally will drop much more quickly than production in exporting countries.
The only reliable way to identify the timing of peak oil will be in retrospect. M. King Hubbert, who devised the peak theory, predicted in 1974 that peak oil would occur in 1995 at 12 gigabarrels per year "if current trends continue". However, in the late 1970s and early 1980s, global oil consumption actually dropped (due to the shift to energy-efficient cars, the shift to electricity and natural gas for heating, etc.), then rebounded to a lower level of growth in the mid 1980s (see chart on right). The shift to reduced consumption in these areas meant that the projection assumptions were not realized and, hence, oil production did not peak in 1995, and has climbed to more than double the rate initially projected.
Colin Campbell of the Association for the Study of Peak Oil and Gas (ASPO) has suggested that the global production of conventional oil peaked in the spring of 2004 albeit at a rate of 23 gigabarrels per year, not Hubbert's 13 gigabarrels per year. During 2004, approximately 24 billion barrels of conventional oil were produced out of the total of 30 billion barrels of oil; the remaining 6 billion barrels coming from heavy oil and tar sands, deep water oil fields, and natural gas liquids (see adjacent ASPO graph). In 2005, the ASPO revised its prediction for the peak in world oil production, again, from both conventional and non-conventional sources, to the year 2010. These consistent upward (into the future) revisions are expected in models which do not take into account continually increasing reserve estimates in older accumulations.
Another peak oil proponent Kenneth S. Deffeyes predicted in his book Beyond Oil - The View From Hubbert's Peak that global oil production would hit a peak on November 25th, 2005 (Deffeyes has since revised his claim, and now argues that world oil production peaked on December 16, 2005).
Texas oilman T. Boone Pickens has stated that worldwide conventional oil production will top out at 84 MB/day (31 BB/yr), while Albert Bartlett paper on Arithmetic, Population, and Energy (exponential growth on a finite resource) gives a different insight into peak oil.
Peak oil is concerned with the production flow of oil measured as the quantity extracted over time. Recoverable reserves are important only in that they must exist before any oil can be extracted and delivered to the market.
Conventionally reservoired crude oil resources comprise all crude oil that is technically producible from reservoirs through a well bore using any primary, secondary, improved, enhanced, or tertiary method. Not included are liquids from mined deposits (tar sands; oil shales) or created liquids (gas-to-liquids; coal-to-liquids).
Oil reserves are classified into categories - proven, probable and possible. Proven reserves are claimed to be "Reasonably Certain" to be producible using current technology at current prices and are intended to be 90% certain of containing the amount specified or more. The "Probable Reserves" category has an intended probability of 50% and the "Possible Reserves" an intended probability of 10%. Some care must be taken with these categories, as the majority of reserves have not been subject to outside audit or examination.
Most of the easy-to-extract oil has been found. Recent oil exploration is being carried out in areas where oil is much more expensive to extract, extremely deep wells, extreme downhole temperatures, environmentally sensitive areas or where high-technology will be required to extract the oil. Oil companies such as Exxon Mobil, Shell, and BP are having to spend more money on oil exploration due to a shortage of drilling rigs, increases in steel, an increase in service charges - like drilling rig rates, and overall increases in costs due to complexity.
In forecasting the date of peak oil — and in testing the validity of Hubbert's theory — one difficulty is the strong opacity surrounding the oil reserves classified as 'proven' (see above). This was best exemplified by the scandal surrounding the 'evaporation' of 20% of Shell's reserves. For the most part, the number of 'proven reserves' are given by the three major players of the oil market: the oil companies, the producer states and the consumer states. All three have an interest to inflate their proven reserves: oil companies may use it to increase their potential worth; producer countries are bestowed a stronger international stature; and governments of consumer countries may use this as a means to foster sentiments of security and stability within their economies and among consumers. Many worrying signs concerning the depletion of 'proven reserves' have emerged in recent years. On the other hand investigative journalist Greg Palast has argued that oil companies have an interest in making oil look more rare than it is in order to justify higher prices.
Unconventional sources, such as heavy crude oil, tar sands, and oil shale are not counted as part of oil reserves. However, oil companies can book them as proven reserves after opening a strip mine or thermal facility for extraction. The three major unconventional oil sources are the extra heavy oil in the Orinoco river of Venezuela, the tar sands in the Western Canada Basin, and the oil shale in the Green River Formation in Colorado, Utah and Wyoming in the United States. It is estimated that these sources account for as much oil as the reserves of the Middle East.
The results of one study suggest that within 15 years all the world’s extra oil supply will likely come from expensive and environmentally damaging unconventional sources. This will mean increasing reliance on these hard-to-develop unconventional sources of energy. Oil extracted from these sources typically contains contaminants such as sulfur, heavy metals and carbon that are energy intensive to extract.
A 2003 article in Discover magazine claimed that we could use thermal depolymerization to manufacture as much oil as we could ever need, out of garbage, sewage, and agricultural waste. The article claimed that the cost of the process was $15 per barrel.  A follow up article in 2006 stated that the cost was actually $80 per barrel. 
The demand side of Peak oil is concerned with the consumption of oil measured as the quantity consumed over time. World crude oil demand has been growing at an annualized compound rate around 2 percent in recent years. Demand growth is highest in the developing world, particularly in the People's Republic of China and India, and to a lesser extent in Africa and South America. Where high demand growth exists it is primarily due to rapidly rising consumer demand for transportation via vehicles powered with internal combustion engines.
The U.S. Department of Energy categorizes national energy use in four broad sectors: transportation, residential, commercial, and industrial. In the United States, in contrast to other regions of the world, about 2/3 of all oil use is for transportation, 1/5 goes to industrial uses, and the remainder goes to residential, commercial and electric energy production.
Most oil is consumed in transportation, approximately 66.6% in the United States and 55% worldwide, World demand for oil is set to increase 37% by 2030, according to the US-based Energy Information Administration's (EIA) annual report. Demand will hit 118 million barrels per day (bpd) from today's existing 86 million barrels, driven in large part by transport needs.
In his 1992 book Earth in the Balance, Al Gore wrote, "... it ought to be possible to establish a coordinated global program to accomplish the strategic goal of completely eliminating the internal combustion engine over, say, a twenty-five-year period..." 
Because of human population growth, oil production per capita peaked in the 1970s. The world’s population in 2030 is expected to double from 1980 and be much more industrialized and oil-dependent than it was in 1980. Some predictions suggest that worldwide oil production in the year 2030 will have declined to the same level as it was in 1980, in which case worldwide demand for oil will significantly outpace its worldwide production. Some physicists maintain that the non-sustainability of oil production per capita was not addressed due to the political correctness implications of suggesting population control.
One factor that may ameliorate this effect is the rapid decline of population growth rate since the 1970s. In 1970, the population growth rate was 2.1%. By 2006, it had declined to 1.1%. Meanwhile, oil production has continued to grow strongly. From 2000 to 2005, human population only grew by 6.3% , whereas global oil production increased by 8.2% .
Supplies of oil and gas are essential to modern agriculture,  so coming decades could see spiraling food prices and massive and unprecedented famine affecting human populations across the globe.  Geologist Dale Allen Pfeiffer contends that to achieve a sustainable economy and avert disaster, the United States must reduce its population by at least one-third, and world population will have to be reduced by two-thirds. Current U.S. population of more than 300 million as well as world population exceeding 6.6 billion are, according to Pfeiffer, unsustainable.
As countries develop, industry, rapid urbanization and higher living standards drive up energy use markedly. The energy supply to drive industrialization mostly comes from oil. For example, thriving economies such as China and India are quickly becoming large consumers of oil. China has seen oil consumption grow by 8% yearly since 2002, (7% annual growth equals a doubling of consumption every 10 years) it currently imports roughly half its oil, with predictions of 14.2 mb/d by 2025. India's oil imports are expected to more than triple to some 5 million barrels a day by 2020. Cars and trucks will cause almost 75% of the increase in oil consumption by India and China between 2001 and 2025. As more countries develop, the demand for oil will increase further.
The effects of peak oil can be mitigated through conservation and finding alternatives 20 years or more before the peak. Because mitigation can reduce the consumption of traditional petroleum sources, it can also affect the timing of peak oil and the shape of the Hubbert curve.
As of July of 2007, analysts still disagree on whether peak production capacity has been reached.
The IEA projects non-OPEC production estimates for 2007 and 2008 to remain largely unchanged from July 2007, at 50.0 mb/d and 51.0 mb/d, respectively. Growth is projected to recede thereafter as the slate of verifiable investment projects diminishes. 
|“||The concept of peak oil production and its timing are emotive subjects which raise intense debate. Much rests on the definition of which segment of global oil production is deemed to be at or approaching peak. Certainly our forecast suggests that the non-OPEC, conventional crude component of global production appears, for now, to have reached an effective plateau, rather than a peak.||”|
The report points to only a small amount of supply growth from OPEC producers, with 70% of the increase coming from Saudi Arabia, the UAE and Angola as security and investment issues continue to impinge on oil exports from Iraq, Nigeria and Venezuela.
Analysts from Wood Mackenzie contend that maximum production of oil will not occur before 2014. Kate Dourian, Platts' Middle East editor, has a different opinion. "Some sources say half the world's oil has already been produced, whereas Saudi Aramco is saying there is still another trillion barrels out there." She is also quick to point out that politics has entered the equation. "Some countries are becoming off limits. Major oil companies operating in Venezuela find themselves in a difficult position because of the resource nationalism that's spreading. These countries are now reluctant to share their reserves"
Matthew Simmons, Chairman of Simmons & Company International, said on October 26, 2006 that global oil production may have peaked in December 2005, though he cautions that further monitoring of production is required to determine if a peak has actually occurred.
In State of the World 2005, Worldwatch Institute observes that oil production is in decline in 33 of the 48 largest oil-producing countries. Other countries have also passed their individual oil production peaks.
World oil production growth trends, in the short term, have been flat over the last 18 months. Global production averaged 85.24 mbbl/d in 2006, up 0.76 mbbl/d (0.9%), from 84.48 mbbl/d in 2005. Production in Q2 2007 was 84.90 mbbl/d, down 0.05 mbbl/d (0.1%), from the same period a year earlier. Average yearly gains in world oil production from 1987 to 2005 were 1.2 mbbl/d (1.7%), with yearly gains since 1997 ranging from -1.4 mbbl/d, (-1.9%; 1998-1999) to 3.3 mbbl/d (4.1%; 2003-2004).
Of the largest 21 fields, about 9 are already in decline.
Mexico announced that its giant Cantarell Field entered depletion in March, 2006, as did the huge Burgan field in Kuwait in November, 2005. Due to past overproduction, Cantarell is now declining rapidly, at a rate of 13% per year. In April, 2006, a Saudi Aramco spokesman admitted that its mature fields are now declining at a rate of 8% per year, and its composite decline rate of producing fields is about 2%. This information has been used to argue that Ghawar, the largest oil field in the world, has peaked.
Many commentators have pointed to the Jack 2 deep water test well in the Gulf of Mexico, announced September 5, 2006, as evidence that there is no imminent peak in global oil production. The Jack 2 field, however, may have at best the potential to provide only 2 years of U.S. consumption at present levels. Peak oil theory does not suggest that there will be no major or minor oil finds in the future, but rather that new discoveries and new production will not be able to offset depletion in other parts of the world. Also, the new fields will be harder to find, harder to get to and harder to extract out the oil. The Jack 2 field, for instance, is more than 20,000 feet under the seafloor in 7,000 feet of water, for a total of 28,000 feet (8.5 kilometers) of pipe.
This increasing investment in harder to reach oil is a sign of oil companies' belief in the end of easy oil:
|“||All the easy oil and gas in the world has pretty much been found," said William J. Cummings, ExxonMobil's spokesman in Angola. "Now comes the harder work in finding and producing oil from more challenging environments and work areas.||”|
Chuck Masters of the United States Geological Survey says:
|“||Unconventional resources, such as extra heavy oils, tar sands, gas in tight sands, and coal bed methane are not considered [in the USGS 2000 assessment] but they must, nonetheless, be recognized as being present in very large quantities. ... The two major sources of unconventional oil ... are the extra heavy oil in the Orinoco province of Venezuela and the ... tar sands in the Western Canada Basin. Taken together, these resource occurrences, in the Western Hemisphere, are approximately equal to the Identified Reserves of conventional crude oil accredited to the Middle East.||”|
These unconventional sources are not as efficient to produce however, requiring extra energy to refine, resulting in higher production costs and up to three times more greenhouse gas emissions per barrel (or barrel equivalent), as analyzed by industry sites such as Rigzone..
Commodities trader Raymond Learsy, author of Over a Barrel: Breaking the Middle East Oil Cartel, contends that OPEC has trained consumers to believe that oil is a much more finite resource than it in fact is. To back his argument, he points to past false alarms and apparent collaboration. He also believes that Peak Oil analysts are conspiring with OPEC and the oil companies to create a "fabricated drama of peak oil" in order to drive up oil prices and profits. It is worth noting oil had risen to a little over $30/barrel at that time. A counter-argument was given in the Huffington Post after he and Steve Andrews, co-founder of ASPO, debated on CNBC in June 2007.
|The neutrality of this section is disputed.|
Please see the discussion on the talk page.
Kate Dorian of Platts said "some oil-rich countries are restricting oil sales outside of their country. These countries are now reluctant to share their reserves" According to consulting firm PFC Energy, only 7% of the world's estimated oil and gas reserves are in countries that allow companies like ExxonMobil free rein. Fully 65% are in the hands of state-owned companies such as Saudi Aramco, and the rest are in the likes of Russia and Venezuela, where access by Western companies is volatile. The PFC study implies political factors are limiting capacity increases in Mexico, Venezuela, Iran, Iraq, Kuwait and Russia. Saudi Arabia is also limiting capacity expansion but because of a self-imposed cap, unlike the other countries. As a result of not having access to countries amenable to oil exploration, ExxonMobil isn't making nearly the investment in finding new oil that it did in 1981.
Mexico nationalized its oil industry in 1938, and has never privatized it, restricting foreign investment. Since the giant Cantarell field in Mexico is now in decline, the state oil company Pemex has faced intense political opposition to opening up the country's oil and gas sector to foreign participation. Some feel that the state oil company Pemex does not have the capacity to develop deep water assets by itself, but needs to do so if it is to stem the decline in the country's crude production.
Major oil companies operating in Venezuela find themselves in a difficult position because of the resource nationalism that's spreading. Exxon Mobil and ConocoPhilips have said they would walk away from their large investment in the Orinoco heavy-oil belt rather than accept tough new contract terms which raise its tax take and oblige all foreign companies to accept minority shares in joint ventures with the state oil company, Petróleos de Venezuela (PDVSA).
Iran, now among the world's leading crude-oil exporters, could become a net importer of oil within the next decade due to rising demand and slow-growing production. As the world's second-biggest proven reserves of oil, it infuriated its people when the government brought in petrol rationing on two hours notice. Due to limited refinery capacity, it has been discouraging gasoline usage. Shortly after the petrol/gasoline rationing, which has reduced demand in some areas by 20%-30%, it announced it will not be producing cars powered only by gasoline.
In Russia, Vladimir Putin's government has pressured Royal Dutch Shell to hand over control of one major project on Sakhalin Island, to Russia's Gazprom in December. The founder of formerly-private Yukos has also been jailed, and the company absorbed by state-owned Rosneft.  Such moves strain the confidence of international oil companies in forming partnerships with Russia.
In 2004, 30 billion barrels of oil were consumed worldwide, while eight billion barrels of new oil reserves were discovered in new accumulations, a number which excludes reserve growth in existing fields. In August 2005, the International Energy Agency reported global demand at 84.9 million barrels per day, resulting in an annual demand of over 31 billion barrels. This means consumption is now within 2 Mbbl/d of production. At any one time there are about 54 days of stock in the OECD system plus 37 days in emergency stockpiles. In June 2005, OPEC admitted that they would 'struggle' to pump enough oil to meet pricing pressures for the fourth quarter of that year. The summer and winter of 2005 brought oil prices to a new high (not adjusted for inflation). On the other hand, some analysts attribute much of this new high to disruptions caused by the war in Iraq.
A combination of factors such as fear of war with Iran and hurricanes caused oil prices to peak at $78.64 on August 7, 2006, followed by falls away from the peak. On September 13, 2007, oil prices hit a new peak of $80.18 and finished the day at $80.08, closing above $80 for the first time since trading on the exchange began, on the back of lower reserve data in the US, generally tight supplies, unrest in Nigeria and Mexico, growing tension with Iran, and a falling US dollar. Production is at or near full capacity.
Oil futures briefly traded over $90.00 per barrel on October 19, 2007. A variety of reasons were given for this new record high oil futures, including a possible incursion by Turkey into Northern Iraq, which could result in oil pipelines in that region being attacked. Another possible explanation is that oil demand is reaching parity with oil supply, and the markets are bidding up the oil futures contracts to higher levels.
An oil price chart can be seen here.
Part of the current debate revolves around energy policy, and whether to shift funding to increasing energy conservation, fuel efficiency, or other energy sources like solar, wind, and nuclear power. For example, in the USA Rep. Tom Udall at congressional peak oil hearings:
|“||Some say that market forces will take care of the peak oil problem. They argue that as we approach or pass the peak of production, the price of oil will increase and alternatives will become more competitive. Following this, consumers will act to replace our need for non-petroleum energy resources. This philosophy is partly true. However, the main problem with this argument is that current U.S. oil prices do not accurately reflect the full social costs of oil consumption. Currently, in the United States, federal and state taxes add up to about 40 cents per gallon of gasoline. A World Resources Institute analysis found that fuel-related costs not covered by drivers are at least twice that much. The current price of oil does not include the full cost of road maintenance, health and environmental costs attributed to air pollution, the financial risks of global warming from increasing carbon dioxide emissions or the threats to national security from importing oil. Because the price of oil is artificially low, significant private investment in alternative technologies that provide a long-term payback does not exist. Until oil and its alternatives compete in a fair market, new technologies will not thrive.||”|
|“||... the federal government could more effectively increase the efficiency of the nation's automotive fleet by raising gasoline taxes, imposing user fees on the purchase of low-mileage-per-gallon vehicles, or both. ...Such policies might also spur more-productive research--because automakers would have a greater incentive not only to conduct research into fuel-cell technology but also to broaden their research efforts to include other potential sources of fuel efficiency, such as more-sophisticated drive trains and transmissions and lightweight but durable chassis and body materials.||”|
A warning of the level of incentive required for market driven research and development is stated by Rogner:
|“||Additionally, production cost reductions will not materialize in the absence of investments. Their magnitude and timing may affect the timing of future access to hydrocarbon resources. The scale of upfront investment requirements is expected to increase while the economic risk associated with upstream hydrocarbon projects will likely be higher than for alternative non-energy investment opportunities (61). Therefore, the quest for short-term profits may well be a road block to long-term resource development.||”|
The problems of privately funded research and development, as espoused by Bronwyn H. Hall, are not unique to peak oil mitigation.
|“||even if problems associated with incomplete appropriability of the returns to R&D are solved using intellectual property protection, subsidies, or tax incentives, it may still be difficult or costly to finance R&D using capital from sources external to the firm or entrepreneur. That is, there is often a wedge, sometimes large, between the rate of return required by an entrepreneur investing his own funds and that required by external investors.||”|
In the US, transportation by car is guided more by the government than by an invisible hand. Roads and the interstate highway system were built by local, state and federal governments and paid for by income taxes, property taxes, fuel taxes, and tolls. The Strategic Petroleum Reserve is designed to offset market imbalances. Municipal parking is frequently subsidized. Emission standards regulate pollution by cars. US fuel economy standards exist but are not high enough to have effect. There is also a gas guzzler tax of limited scope. The United States offers tax credits for certain vehicles and these frequently are hybrids or compressed natural gas cars, see Energy Policy Act of 2005.
In order to be profitable, many alternatives to oil require the price of oil to remain above some level. So investors in these alternatives must gamble with the limited data on oil reserves available. This imperfect information can lead to a market failure caused by a move by nature; for instance see Hotelling's rule for non-renewable resources. Even with perfect information the price of oil correlates with spare capacity and spare capacity does not warn of a peak:
|“||To put this into perspective, in 2004 world oil production is 80 Mb/d; spare capacity would need to be 44 Mb/d to be equivalent to US conditions in 1962. To predict that US production would peak in less than ten years given this much spare capacity seemed at the very least completely unrealistic to most people.||”|
Lester Brown believes this problem might be solved by the government establishing a price floor for oil. A tax shift raising gas taxes is the same idea. Opponents of a price floor for oil argue that the markets would distrust the government's ability to keep the policy when oil prices are low.
|It has been suggested that this article or section be merged with Peak_oil#Timing. (Discuss)|
Not all non-'peakists' believe there will be endless abundance of oil. CERA, for example, instead believes that global production will eventually follow an “undulating plateau” for one or more decades before declining slowly. In 2005 the group had predicted that "petroleum supplies will be expanding faster than demand over the next five years."
The U.S. Energy Information Administration projects world consumption of oil to increase to 98.3 million barrels a day in 2015 and 118 million barrels a day in 2030. This represents more than a 25% increase in world oil production. A 2004 paper by the Energy Information Administration based on data collected in 2000 disagrees with Hubbert peak theory on several points:
The EIA estimates of future oil supply are countered by Sadad Al Husseini, retired VP Exploration of Aramco, who calls it a 'dangerous over-estimate'. Husseini also points out that population growth and the emergence of China and India means oil prices are now going to be structurally higher than they have been.
Campbell argues that the 2000 USGS estimates is methodologically flawed study that has done incalculable damage by misleading international agencies and governments. Campbell dismisses the notion that the World can seamlessly move to more difficult and expensive sources of oil and gas when the need arises. He argues that oil is in profitable abundance or not there at all, due ultimately to the fact that it is a liquid concentrated by nature in a few places having the right geology. Campbell believes OPEC countries raised their reserves to get higher oil quotas and to avoid internal critique. He also points out that the USGS failed to extrapolate past discovery trends in the world’s mature basins.
Some commentors, such as economists Michael Lynch and Michael Moffat, believe that the Hubbert Peak theory is flawed and there is no imminent peak in oil production; such views are sometimes referred to as "cornucopian" by believers in Hubbert Peak Theory. Lynch argues that production is determined by demand as well as geology, and that fluctuations in oil supply are due to political and economic effects in addition to the physical processes of exploration, discovery and production. Moffat contends that as prices increase, consumers will find alternatives to gasoline. Changes in consumer patterns and the emergence of new technology driven by increases in the price of oil will prevent the oil supply from ever physically running out.
Biogenesis remains the overwhelmingly majority theory among petroleum geologists in the United States. Abiogenic theorists, such as the late professor of astronomy Thomas Gold at Cornell University, assert that the sources of oil may not be “fossil fuels” in limited supply, but instead abiotic in nature. They theorize that if abiogenic petroleum sources are found to be abundant, it would mean Earth contains vast reserves of untapped petroleum. However, M. R. Mello and J.M. Moldowan counter that biomarkers show that 99.99999% of all the oil and gas accumulations found up to now on earth have a biologic origin, and that oil is generated from kerogen by pyrolysis.
Although the finiteness of the earth's oil supply means that peak oil is inevitable, technological innovations in finding and drillng for oil have delayed the appearance of peak oil on several occasions. For example, the National Center for Policy Analysis states: 
None of this means that new oil is forming, or that peak oil will never happen. It means that newer technological advances allow us to find and recover more oil, though later estimates are based on unaudited claims by countries that withhold field production data and are therefore inconclusive.