We got the answer moments ago, when the Treasury unveiled it would increase auction sizes for 3, 10 and 30 Year maturities and will increase other maturities, FRNs over the quarter.

Specifically, the Treasury will offer $66 billion of Treasury securities - up from $62 billion last quarter - to refund approximately $46.6 billion of privately-held Treasury notes maturing on February 15, 2018. The securities are:

Treasury to sell $26b of three-year notes vs $24b in Nov.
Treasury to sell $24b of 10-year notes vs $23b from Nov.
Treasury to sell $16b of 30-year bonds vs $15b Nov. level
Why is this important? Because it goes to supply, of which there will be plenty in 2018, in fact as Goldman calculated earlier this month, net Treasury issuance is set to double from $488BN to over $1Tn this year. And if there isn't enough demand, it will mean that rates have to rise, perhaps sharply.