This chapter tackles the ongoing debate about the Great Divergence, much of which revolves around the reliability and representativeness of the economic data used and the parameters they generate. Despite China’s extremely long tradition of Confucian education, literacy rates, imperial bureaucracy and record-keeping, trustworthy data—be they community outputs and prices, cadastral surveys and population censuses—are in fact hard to obtain. This chapter explores some of the fundamental problems with China’s historical records that render them incompatible with, and unsuited for, modern data compilation and analysis. Thus, it is difficult to compare China with Europe (or a region of China with a region of Europe) without encountering huge margins of error. The chapter provides appendices relating to the problematic aspects of some of the statistical data used in historical estimations of Chinese national income.