Although multinational corporations dominate Ireland's export sector, exports from other sources also contribute significantly to the national income. The activities of multinational companies based in Ireland have made it one of the largest exporters of pharmaceutical agents, medical devices and software-related goods and services in the world. Ireland's exports also relate to the activities of large Irish companies (such as Ryanair, Kerry Group and Smurfit Kappa) and exports of mineral resources: Ireland is the seventh largest producer of zinc concentrates, and the twelfth largest producer of lead concentrates. The country also has significant deposits of gypsum, limestone, and smaller quantities of copper, silver, gold, barite, and dolomite. Tourism in Ireland contributes about 4% of GDP and is a significant source of employment.