Can a population-declining Japan sustain growth?

Modern Japan’s population and GDP underwent three stages of transition: the prewar stage (1878–1939), postwar stage (1950–2008), and postmodern stage (after 2009). By means of a simple ARIMA model, I predict Japan’s GDP will decline considerably if Japan stays on the postwar paradigm toward 2100. However, I will show that if Japan can restore the historical trend of 1878–2015, its GDP will grow at around 2% per annum toward 2100. To achieve such a transition, the nation will require dramatically reduced population elasticity, and a faster rate of X-efficiency increase, including technological and institutional transformations.