The major reason for the unusually low long-term real interest rates appears to be a high level of desired savings relative to desired investment. Interestingly, despite ample (or perhaps overly ample) global liquidity – which historically has led to rising inflation – inflation has been fairly well contained around the globe.
Central banks have been keeping their eyes on inflation and have not hesitated to raise policy rates as required. Parenthetically, I would add that a number of other developments – developments that did not really contribute to global macroeconomic liquidity – may have left the impression that there was a "wall of liquidity" out there.