In what ways did tang and song dynasty china resemble the classical han dynasty period, and in what ways had china changed?

Tang and Song dynasty China resembled the Han dynasty period in a number of ways, including the maintenance of the imperial political system, and the importance of a professional bureaucracy formally trained and subject to competitive exams.
 Also similar was a focus on establishing a dominant political position in East Asia that was recognized by China’s neighbors; an interest in and support for long-distance trade; and the continued importance of the Confucian tradition in elite society. 
China also experienced important changes following the Han dynasty period,including tighter unification of northern and southern China through a vast waterway system; the long-term migration of Chinese populations south into the Yangzi River valley after 220 C.E.; and an economic revolution that made it the richest empire on earth.
There was rapid population growth, from 50 million to 60 million people during the Tang dynasty to 120 million people by 1200, which was spurred in part by a remarkable growth in agricultural production.
 Also, the economy of China became the most highly commercialized in the world and became more active in long-distance trade than during the Han dynasty.