[deafcalculus]

Pension funds are required to own some percentage of their assets in govt bonds. Also, many high net worth individuals have a strong preference for safe assets like govt bonds. And then there are speculators who think interest rates will fall and they'll make killing by actively trading on long term bonds. So, there will be buyers. Not all of it is being purchased by central banks.

[dharma1]

true, there are some free market participants but central banks such a big % of the buyers that if they stopped buying, rates would shoot through the roof

[deafcalculus]

I'm not so sure about that. When the Fed was tapering and starting to raise rates back in 2018, the bond market flashed warning signs in December 2018 with long term rates falling sharply and the yield curve inverting.

Then there's also the market expectations of whether the Fed is willing to go with negative interest rates, which would influence the behavior of bond traders.