This is a random idea that is almost surely wrong. And if it is wrong, it will be wrong in a way that seems obviously stupid. So don’t expect me to stick with it.
Without blaming Nick Rowe, I started thinking about this when he wrote,
By “secular stagnation” I mean “declining equilibrium real interest rates”.
Most explanations of secular stagnation say it is caused by a rising desire to save and/or a falling investment demand. Call this the “Saving/Investment Hypothesis”.
But there are lots of different real interest rates. For example, the real interest rate on Bank of Canada currency is around minus 2%. (That currency pays 0% nominal interest, and the Bank of Canada targets 2% inflation). But people are willing to hold currency, despite that, because it is very liquid. But all assets differ in their liquidity. More liquid assets will have a lower real yield than less liquid assets. And if an asset becomes more liquid over time, its real yield will fall over time.
What if there is a sharp rise in the supply of government debt? The standard view is that this tends to raise interest rates, as debt absorbs more savings.
The alternative view I am putting out there is that government debt offers liquidity (in the limiting case, think of it as a very close substitute for money). If the supply of liquidity goes up, then there is less demand for banks to manufacture liquidity out of risky assets. The public wants fewer deposits backed by loans on fruit trees and instead is happy to hold mutual funds containing government bonds.
The result is fewer fruit trees planted. We would observe a decline in interest rates on low-risk assets and an increase in interest rates (or a loss of credit availability altogether) for risky investment projects.
Think of this as government debt crowding out private investment, even though the interest rate on safe assets, particularly government debt itself, can remain low and perhaps even fall as the crowding out gets larger. Again, this is probably wrong.