Retail gasoline prices fluctuate mainly because of crude oil prices and the level of supply relative to demand. Because of the strong and increasing demand for gasoline in the U.S. and throughout the world, there is a limited supply which increases the price of gas. Prices usually rise slightly in the spring and peak in late summer when people drive more and then drop in the winter. According to the EIA, good weather and vacations cause U.S. summer gasoline demand to average about 5% higher than the rest of the year, causing gas prices to increase by 10-20 cents from January to the end of summer. Crude oil prices are determined by worldwide supply and demand which is why as countries around the world develop rapidly, the demand for and price of gas increases rapidly. Natural disasters and Political conflicts in major oil producing regions such as Saudi Arabia, Iran and Iraq can also affect the price of gas. The Organization of Petroleum Exporting Countries (OPEC) also has significant influence over the price of crude oil because its members produce over 40% of the world’s supply of oil and own more than two-thirds of the world’s estimated oil reserves. Because OPEC members want to maximize their profits, it is often in their best interest to limit the production level as much as possible. States further away from the Gulf Coast (where almost half of the gasoline in the U.S. is produced) tend to have higher oil prices because they are also paying for the cost of transporting the gas from the refinery. Because of this, gas is often higher on the West Coast and near the Rocky Mountain region. Some retailers also try to maximize their profits by raising prices during peak times. Some states have moved to regulate such practices. Gas is often more expensive in areas with few retail gas stations or in areas with low traffic. Areas with a concentrated number of states may