and vinyl manufacturers produce products shipped all over the world, and Edmonton's oil refineries provide the raw materials for a large petrochemical industry to the east of Edmonton. Since the early 1940s, Alberta had supplied oil and gas to the rest of Canada and the United States. The Athabasca River region produces oil for internal and external use. The Athabasca Oil Sands contain the largest proven reserves of oil in the world outside Saudi Arabia. The Athabasca Oil Sands (sometimes known as the Athabasca Tar sands) have estimated unconventional oil reserves approximately equal to the conventional oil reserves of the rest of the world, estimated to be . With the development of new extraction methods such as steam-assisted gravity drainage (SAGD), which was developed in Alberta, bitumen and synthetic crude oil can be produced at costs close to those of conventional crude. Many companies employ both conventional strip mining and non-conventional in situ methods to extract the bitumen from the oil sands. With current technology and at current prices, about of bitumen are recoverable. Fort McMurray, one of Canada's fastest growing cities, has grown enormously in recent years because of the large corporations which have taken on the task of oil production. As of late 2006 there were over $100 billion in oil sands projects under construction or in the planning stages in northeastern Alberta. Another factor determining the viability of oil extraction from the oil sands was the price of oil. The oil price increases since 2003 made it more than profitable to extract this oil, which in the past would give little profit or even a loss. Alberta's economy was negatively impacted by the 2015-2016 oil glut with a record high volume of worldwide oil inventories in storage, with global crude oil collapsing at near ten-year low prices. The United States doubled its 2008 production levels mainly due to substantial improvements in shale "fracking" technology, OPEC members consistently exceeded their production ceiling, and China experienced a marked slowdown in economic growth and crude oil imports. Mining and Oil and Gas Extraction Industry (2017) Data Source: Statistics Canada, Labour Force Survey, CANSIM Table 282–0008, 2017 "Employment share is obtained by dividing the number of employment in this industry by total employment in Alberta." Natural gas Natural gas has been found at several points, and in 1999, the production of natural gas liquids (ethane, propane, and butanes) totalled , valued