rates since the 1960s and increasing reserves by the phenomenon of reserve growth. The report noted that increased reserves within a field may be discovered or developed by new technology years or decades after the original discovery. But because of the practice of "backdating", any new reserves within a field, even those to be discovered decades after the field discovery, are attributed to the year of initial field discovery, creating an illusion that discovery is not keeping pace with production. Reserves Total possible conventional crude oil reserves include crude oil with 90% certainty of being technically able to be produced from reservoirs (through a wellbore using primary, secondary, improved, enhanced, or tertiary methods); all crude with a 50% probability of being produced in the future (probable); and discovered reserves that have a 10% possibility of being produced in the future (possible). Reserve estimates based on these are referred to as 1P, proven (at least 90% probability); 2P, proven and probable (at least 50% probability); and 3P, proven, probable and possible (at least 10% probability), respectively. This does not include liquids extracted from mined solids or gasses (oil sands, oil shale, gas-to-liquid processes, or coal-to-liquid processes). Hubbert's 1956 peak projection for the United States depended on geological estimates of ultimate recoverable oil resources, but starting in his 1962 publication, he concluded that ultimate oil recovery was an output of his mathematical analysis, rather than an assumption. He regarded his peak oil calculation as independent of reserve estimates. Many current 2P calculations predict reserves to be between 1150 and 1350 Gb, but some authors have written that because of misinformation, withheld information, and misleading reserve calculations, 2P reserves are likely nearer to 850–900 Gb. The Energy Watch Group wrote that actual reserves peaked in 1980, when production first surpassed new discoveries, that apparent increases in reserves since then are illusory, and concluded (in 2007): "Probably the world oil production has peaked already, but we cannot be sure yet." Concerns over stated reserves Sadad Al Husseini estimated that of the world's of proven reserves should be recategorized as speculative resources. One difficulty in forecasting the date of peak oil is the opacity surrounding the oil reserves classified as "proven". In many major producing countries, the majority of reserves claims have not been subject to outside audit or examination. Several worrying signs concerning the depletion of proven reserves emerged in about 2004. This was