From the minutes of the Treasury Borrowing Advisory Committee meeting yesterday
"The Committee commented on the demand for ultra-long debt, noting that the regular and predictable issuance policy should remain the central consideration to minimize Treasury’s funding cost over time. While an ultra-long is most likely to be demanded by those with longer-dated liabilities, The Committee recommended that further work be done to study these demand dynamics to get a better sense of where an ultra-long bond might price, which could be above or below the longest maturity debt issuance based on the pricing of domestic ultra-long derivatives, ultra-long bonds abroad, and theoretical models.
