The highest level of Shang society included the royal family and noble warriors. The middle level of the hierarchy was for Artisans. The lowest level were the peasants, and most of the Shang Dynasty population. During the Zhou Dynasty the hierarchy was much stricter and was now called feudalism. During the Zhou Dynasty, China’s economy grew. The Chinese learned of Iron working, which led to more food being produced, as iron tools replaced stone, wood and bronze. It also, led to new crops being able to grow. Trading became a large part of China's economy after the invention of the Silk Road causing trading to be the biggest reason for economic growth. China had many achievements in its time. In early China, the Chinese made the discovery of silk, they wove this material into smooth cloth, that many royals and nobles desired making silk China’s most valuable export. China established a system of writing, that involved thousands of characters that in the early ages only the wealthy could afford the years of study it would take to understand the complex writing. During the Zhou Dynasty, the Chinese had made the first books, made out of thin strips of wood and bamboo together and, then they carefully drew complex characters on the flat surface with