Are we able to explain the considerable decline in the real long-term interest rate in OECD countries?

The real long-term interest rate in OECD countries has declined sharply since the 1980s. What accounts for this decline? It has been much sharper than the decline in potential growth . We can imagin e the following explanations: A larger rise in private savings than in fiscal deficits; A small investment need; The highly expansionary monetary policies; A decline in uncertainty over future interest rates and therefore a fall in the term premium. The pertinent explanations seem to be the rise in private savings, the decline in the investment rate and the expansionary monetary policies.