Advanced economies tend to slide down to zero interest rates and stay there. Why? Advanced economies (e.g., Japan, USA, Europe) tend to slide down to zero interest rates and stay there. Why? Are there any theories which explain this tendency?
Recently I read an interesting paper on this subject from the Bank for International Settlements:

Juselius, Mikael and Takats, Elod, Can Demography Affect Inflation and Monetary Policy? (February 2015). BIS Working Paper No. 485. Available at SSRN: http://ssrn.com/abstract=2562443

The abstract:


  Several countries are concurrently experiencing historically low inflation rates and
  ageing populations. Is there a connection, as recently suggested by some senior
  central bankers? We undertake a comprehensive test of this hypothesis in a panel of
  22 countries over the 1955–2010 period. We find a stable and significant correlation
  between demography and low-frequency inflation. In particular, a larger share of
  dependents (ie young and old) is correlated with higher inflation, while a larger
  share of working age cohorts is correlated with lower inflation. The results are
  robust to different country samples, time periods, control variables and estimation
  techniques. We also find a significant, albeit unstable, relationship between
  demography and monetary policy.


As I'm not an expert on the subject, it is probably not the main explanation in literature but it's in my opinion an interesting research path.