because the import quota prevents domestic consumers from buying an imported good, the supply of the good is no longer perfectly elastic at the world price. Instead, as long as the price of the good is above the world price, the license holders import as much as they are permitted, and the total supply of the good equals the domestic supply plus the quota amount. The price of the good adjusts to balance supply (domestic plus imported) and demand. The quota causes the price of the good to rise above the world price. The imported quantity demanded falls and the domestic quantity supplied rises. Thus, the import quota reduces the imports.
Because the quota raises the domestic price above the world price, domestic sellers are better off, and domestic buyers are worse off. In addition, the license holders are better off because they make a profit from buying at the world price and selling at the higher domestic price. Thus, import quotas decrease consumer surplus while increasing producer surplus and license-holder surplus.
While import quotas and other foreign trade policies can be beneficial to the aggregate domestic economy they tend to be most beneficial, and thus most commonly promoted by, domestic firms facing competition from foreign imports. Domestic firms benefit with higher sales, greater profits, and more income to resource owners. However, by increasing domestic prices and restricting accessing to imports, foreign trade policies also tend to be harmful to domestic consumers.