u21.
For instance, John King Fairbank and Merle Goldman (1992) write, “An estimated population of 60 million as of AD 2 in mid-Han had been matched by roughly the same figure in mid-Tang, suggesting a thousand years of ups and downs with only a modest overall increase.” China: A New History, p 167. For the usual sense of “steady state economy”, see, e.g., Herman E. Daly (1992), Steady-State Economics.