At the beginning of the first millennium in the Western calendar, China was in the midst of the 400-year-long Han dynasty (206 BC to 220 AD), while in the West Rome was making the transition from a republic to an empire that would last until 476 AD. Coincidentally, the two empires had roughly the same population, about 50 million people.
兩漢國祚共四百多年（BC206－AD220），同時期西方羅馬逐漸從共和走上帝國（BC18－AD476），巧的是，除了同樣是疆界遼闊的大國，漢代人口有五千多萬，與羅馬帝國人口不相上下。