Over the past 12 months, for example, the yuan has risen nearly 15% against the yen. That has put pressure on Chinese manufacturers to cut prices; the Chinese producer-price index has fallen for 30 consecutive months, the longest decline since the late 1990s. In turn, that puts further downward pressure on American inflation; since 1995, there has been a 70% correlation between Chinese producer prices and American consumer prices, according to Deutsche Bank.
If other central banks in the developed world respond to the yen depreciation by loosening monetary policy, then the net effect on economic growth would be positive. But the Fed and the Bank of England have stopped easing and the European Central Bank seems reluctant to adopt QE. The extra burst of Japanese QE may only offset a planned rise in the consumption tax, so the net effect on global demand could be zero.