China is geographically divided into two parts - an inner agricultural region where 95% of people live, and an outer sparsely populated region of mountains, plateaus, deserts and steppes. The population of over 1 billion people makes China the most populous country in the world, though only 4% of its land can be cultivated. Under Communist rule in the 20th century, collective farms were established to increase agricultural production. Since economic reforms in the late 1970s, China has experienced rapid economic growth and development, becoming the world's second largest economy through industrialization, international trade, urbanization and investment.