Plastic bottles are ubiquitous but the cost of producing them varies dramatically around the world, thanks mainly to differences in raw-material costs and energy prices. The main type of plastic used, polyethylene terephthalate (PET), is made from naphtha, an oil derivative, which can be partly substituted with ethane, a natural-gas derivative. Very little ethane is traded internationally, so only places where natural gas is cheap and abundant use it to make PET. Because of its shale-gas boom, these now include America as well as the Middle East. Europe and Asia rely only on expensive naphtha. In these places the higher cost of fuel and electricity also push up production costs for plastic bottles.