In the struggle to explain this year's collapse in volatility and volume in financial trading, one newly-nominated culprit is central banks' intent to use every tactic available short of raising interest rates too soon. It sounded like a deeply contrarian view on Friday after comments by Bank of England Governor Mark Carney, but a study by analysts from market heavyweights HSBC this week argued that the use of macroprudential steps will make central bank interest rates in general less volatile in future. Implicitly that may mean markets see less marked swings. The global economy is right at the point, as the economic fates of Japan, Europe and the United States diverge, when an upturn in trading action could be expected due to the growing chances for arbitrage between future interest rates. Yet volatility, which traders depend upon for profits, is at rock bottom. Trading in currencies on the biggest platforms has fallen by a third to half in the past year; options contract