It is a fact that since the mid 1990s interest rates in the world started a downward trend. This trend was explained by Ben Bernanke in his March 2005 speech
“To be more specific, I will argue that over the past decade a combination of diverse forces has created a significant increase in the global supply of saving--a global saving glut--which helps to explain the relatively low level of long-term real interest rates in the world today”
This can easily be represented in a standard demand and supply chart for the global market for funds where the saving glut is simply a shift of the saving (supply) curve to the right.
What was interesting about the saving glut hypothesis is that it not only explained the decrease in interest rates but it was also able to account for the growth in global imbalances. One simple way to represent that is to separate the world in two blocks: those whose saving increased and the rest of the world. We can use again a simple demand and supply chart to represent this two group of countries: we represent the countries whose saving was increasing on the left hand side and the rest of the world on the right hand side to get the following picture:
This shows that we should expect the countries that increase their saving to display a growing current account surplus and the countries where the two curves are not shifting to display a growing current account deficit. This simple framework matches well the data during those years. Current account surplus in countries such as Germany, Japan, Oil producing countries, China and other emerging markets in Asia increased while deficits in countries such as the US and Greece, Spain, Portugal, Ireland, the UK increased as well. Here is the data (from the IMF World Economic Outlook):
But in this story there were some predictions that were never tested. In particular, as interest rates fell, investment should have increased globally. If you look at the saving and investment curves above, investment should have increased both in countries where the supply of saving was shifting as well as in the other countries. Unless we believe that investment rates do not depend on the interest rates we should have seen a generalized increased in investment around the world. Did we see that? No. In fact in advanced economies (including the US, as I showed yesterday) we have seen the opposite. Below is a chart that I have constructed using data from the IMF (World Economic Outlook database). I have calculated the aggregate investment rate (as % of GDP) for all advanced economies using the GDP share of each of these countries as weights [using PPP adjusted weights makes no difference for these countries].
There is a clear downward trend in the data. Even if we ignore the post-2008 data. the expansion in the 2000s was weaker that that of the 90s or the 80s. And remember that we expected exactly the opposite. The only way to make this last chart compatible with the saving glut story is to argue that at the same time that the saving curve was shifting to the right in some countries, the investment curve was also shifting (this time inwards) in other countries.
The shift of the investment curve would also help explain the lower interest rate during the decade. But in addition it would explain why growth rates (and labor market performance) remained weak during the expansion of the 2000s in some advanced economies. And given what we have seen so far during the current expansion it might be a source of additional pessimism about the coming years.
Antonio Fatás