for production is estimated to be equivalent to 7% of the gross energy produced today, and 24% for 2050. Anticipated production by major agencies Average yearly gains in global supply from 1987 to 2005 were (1.7%). In 2005, the IEA predicted that 2030 production rates would reach , but this number was gradually reduced to . A 2008 analysis of IEA predictions questioned several underlying assumptions and claimed that a 2030 production level of (comprising of crude oil and of both non-conventional oil and natural gas liquids) was more realistic than the IEA numbers. More recently, the EIA's Annual Energy Outlook 2015 indicated no production peak out to 2040. However, this required a future Brent crude oil price of $US144/bbl (2013 dollars) "as growing demand leads to the development of more costly resources". Oil field decline In a 2013 study of 733 giant oil fields, only 32% of the ultimately recoverable oil, condensate and gas remained. Ghawar, which is the largest oil field in the world and responsible for approximately half of Saudi Arabia's oil production over the last 50 years, was in decline before 2009. The world's second largest oil field, the Burgan Field in Kuwait, entered decline in November 2005. Mexico announced that production from its giant Cantarell Field began to decline in March 2006, reportedly at a rate of 13% per year. Also in 2006, Saudi Aramco Senior Vice President Abdullah Saif estimated that its existing fields were declining at a rate of 5% to 12% per year. According to a study of the largest 811 oilfields conducted in early 2008 by Cambridge Energy Research Associates, the average rate of field decline is 4.5% per year. The Association for the Study of Peak Oil and Gas agreed with their decline rates, but considered the rate of new fields coming online overly optimistic. The IEA stated in November 2008 that an analysis of 800 oilfields showed the decline in oil production to be 6.7% a year for fields past their peak, and that this would grow to 8.6% in 2030. A more rapid annual rate of decline of 5.1% in 800 of the world's largest oil fields weighted for production over their whole lives was reported by the International Energy Agency in their World Energy Outlook 2008. The 2013 study of 733 giant fields mentioned previously had an average decline rate 3.83% which was described as "conservative." The