Regional economic groups allow countries in a particular region to establish common trade rules and regulations. This promotes trade by reducing barriers between member countries through free trade areas and customs unions. When countries form regional trade groups, it can increase national income through increased trade (trade creation) but may also divert trade away from non-member countries (trade diversion). Regional groups have grown in recent decades and now account for over a third of global trade. They are seen as important forms of increasing trade between both developed and developing countries to support economic growth.