Very interesting. I didn't know that about Qing China. It makes sense considering the upheaval throughout that period.
Yes, but at the same time Qing's population was actually decreasing throughout the latter half of the 19th century after hitting a peak in the 1840s, and only from the 1890s did population started going up. In addition, the 1909-1911 stats I mention actually understates the population, since there was a more than 10% difference between that estimate and the 1912 official census data. In other words, the number I calculated is a reasonable estimate.
1909-1911 Estimates and 1912 Census, based on "China Economic Yearbook" (1934).