The usage and pricing of gasoline (or petrol) results from factors such as crude oil prices, processing and distribution costs, local demand, the strength of local currencies, local taxation, and the availability of local sources of gasoline (supply). Since fuels are traded worldwide, the trade prices are similar. The price paid by consumers largely reflects national pricing policy. Most countries impose taxes on gasoline (petrol), which causes air pollution and climate change; whereas a few, such as Venezuela, subsidize the cost. Some country's taxes do not cover all the negative externalities, that is they do not make the polluter pay the full cost. Western countries have among the highest usage rates per person. The largest consumer is the United States.