That is, they reflect the markets’ view of the real cost of borrowing that can be sustained by an economy that is neither overheating nor decelerating. Indeed, barring preferred habitat and extreme price inelasticities on the side of potential sellers, at those maturities all shocks should have dissipated, and the economy should be expected to have returned to a sustainable path.
This interpretation is less benign than the first one I advanced. If one interprets long-term real forward rates as a measure of the equilibrium rate, the comparison of these persistently negative rates with the growth rate of potential suggests that the economy may be dynamically inefficient and expected to remain so for a very long time.