Nonetheless, the structure of the world rice market together with regular major government interventions in rice trade make the rice market inherently more unstable than world markets for maize and wheat. There is substantial concentration among rice exporters—the five largest exporters accounting for four-fifths of the trade—and, as a result, production or policy shocks in one or more of these countries have major effects on world prices and trade volumes. Moreover, the role of national govern- ments in the conduct of world rice trade is generally greater than for wheat and maize trade, as many rice-importing countries provide their domestic producers with high protection, and state traders play major roles in several key exporting and importing nations. Instability is also increased by the segmentation of the world rice market into submarkets, including medium-/short-grain rice imported mainly by Japan and Korea, high-value aromatic rice (such as basmati and jasmine), nonaromatic long-grain rice, and broken rice.