Low fertility rates, mortality outstripping the birth rate and population contraction characterize a new demographic transition (the so-called "fifth stage"). This paper seeks to evaluate how this phenomenon has impacted the Japanese economic structure and overall productivity. We test two key mechanisms that have been at play since the mid-2000s: i) a growing complementarity between goods and services consumption, and ii) the substitution of older workers engaged in routine tasks with technological capital. According to Autor and Dorn's (2013) model, this should promote the concentration of low-skilled workers in the service sector, and aggravate productivity gaps between industry and services. Using stochastic frontier models and EU-KLEMS data, we compute industry-by-industry TFP growth frontiers in order to check if theoretical predictions match with Japanese reality.