According to a US Study from May 2007, between  and  of Iraq's declared oil production over the past four years could have been siphoned off through corruption or smuggling. In 2008, Al Jazeera reported $13 billion of Iraqi oil revenues in US care was improperly accounted for, of which $2.6 billion is totally unaccounted for. Some reports that the government has reduced corruption in public procurement of oil; however, reliable reports of bribery and kickbacks to government officials persist.