According to the World Tourism Organization, the largest industry of the current world is not automobile and petroleum but tourism. As early as the beginning of 1990s, the economic aggregate of tourism accounted for more than 10% of the world's GDP, and its number of employed people amounted to over 8% of the total global employment. Tourism has superseded automobile and petroleum as the largest industry in the world. It has increasingly become an important symbol of modern economy and social development.