The concept of Produced-to-date or cumulative Production is straightforward - how much has been produced. It is however necessary to watch out for territorial changes and the treatment of war loss, as in Kuwait (2.5 Gb), which in principle should be regarded as production, although in this case is ignored as being small in relation to the uncertainty of the reserves. North America and the Middle East Gulf have produced the most, at just under 190 Gb, with Eurasia in third place. In terms of individual countries, the United States heads the list (171 Gb), followed by the FSU (125 Gb) and, far behind in third place, Saudi Arabia with 74 Gb. This illustrates the maturity of the United States, which for many years in the past was the world's most important producer.