There are two quite different but not incompatible reasons for secular stagnation. The first concerns the "supply side" of an economy. Its capacity to grow may become impaired, for example, through a decline in the growth of the labor force that is compensated for by increases in labor productivity. The latter factor in turn may arise because productivity-increasing investment has reached limits and/or measurable technical improvements in products and production processes are also limited. This seems to have been the case in Japan, where the labor force has declined for some years.