This paper explains that the interest rate on long-term Japanese government bonds is low in comparison with other industrialised countries for four main reasons: lower inflation, net savings surplus, institutional restrictions and home bias. Monetary policy and institutionalised purchases of government bonds by semi-government agencies keep the market demand for bonds high. We find that since the 1970s Japanese interest rate movements are better explained by the current account balance than in other industrialised countries. This is caused by sizeable net oversavings and institutional reasons increased the impact of oversavings as such on the long-term interest rate for Japan. Hence, the institutional reasons increase the coefficient value of the savings-investment balance. A reason for the existence of the high national net savings surplus could be that unsustainable budgetary deficits in Japan called for a Ricardian response. We doubt whether Ricardian equivalence is here the driving factor: household savings have actually fallen over the nineties. Corporate savings, in response to overcapacity and poor investment outlook, have risen more strongly. This has kept the private and national savings balance positive. There is also some indication that ageing has contributed to the structural current account surplus for Japan.