[rubber_duck]

I'd guess there is there is too much money in it due to the fact that central banks killed interest rates and started buying government bonds as needed - where pension funds would hold those they now need to search positivie returns and there's just not enough good bets there - would explain why the valuations are sky high

[MiroF]

You've confused cause and effect.

Declining expectations for NGDP growth/uncertainty lead to funds searching for yield in the credit markets, leading to declining yields.

Bond yields declined prior to Fed intervention [0]

[0]: https://fred.stlouisfed.org/series/DGS10

[di4na]

more due to the fact we massively move retirement payments to market investment instead of redistribution and at the same time boomer begun retiring.

Basically we moved back to a renting society.