Long run real interest rates
The (central) Bank of Canada published the best-evidenced paper I could find on determinants of real interest rates. Historical data shows interest rates are most affected by slow-moving changes, notably in labour force growth and demographic dependency ratios. Systemic changes can also be important, specifically financial innovation and increased risk/leverage in recent years. Finally, global shocks (eg oil prices, sovereign default risk, financial crisis response policies) have sometimes over-ridden the long term trends.
The paper also notes that long-run averages of real interest rates across countries have converged over the past quarter of a century, due to an increasingly financially integrated world, reduced capital controls and the rising scale of speculative financial betting on global futures. As a result, it is now harder for individual countries to control their economic environment.
This 2010 paper concludes interest rates are unlikely to rise significantly in the future since most of the key variables tend to change slowly. I’d suggest that new systemic shocks are not far away, and risk will re-emerge as a driver of interest rates in nations with enduring economic weaknesses.