How the Treasury Market Works

Almost every rate in finance is priced relative to US Treasuries — a corporate bond yield is "Treasuries plus a spread," a mortgage rate tracks the 10-year, a swap rate references the curve. None of that works unless Treasuries themselves trade in a deep, orderly market. That market is not one venue; it is a chain of three connected pieces, and a problem anywhere in the chain shows up as stress everywhere else.

The three layers

Primary market. The Treasury issues new debt through regular auctions — bills, notes, and bonds sold competitively to primary dealers, banks, and increasingly direct investors. This is covered in depth elsewhere; what matters here is that auctions set the coupon and the starting price for every bond that will later trade.

Secondary market. Once issued, a Treasury trades for years afterward, mostly over-the-counter through primary dealers and increasingly on electronic interdealer platforms. The newest issue of a given maturity — the on-the-run bond — trades far more actively than older, off-the-run bonds of similar maturity, simply because it is the one everyone is quoting and hedging with.

Financing market. Owning a bond outright ties up cash. The repo market lets a holder post the bond as collateral and borrow cash overnight against it, or lets a short-seller borrow the bond itself. This financing layer is what makes it possible for dealers to hold large inventories and for leveraged investors to run big Treasury positions at all.

Worked example: why on-the-run trades tighter

A newly auctioned 10-year note trades at a bid-ask spread of roughly 0.5 basis points in yield. A 10-year note issued eighteen months ago, now off-the-run, might trade at 1.5–2 basis points. On a $10 million position, that difference is worth roughly $1,000–$1,500 in transaction cost — not because the off-the-run bond is riskier, but because fewer participants are actively quoting it, so a dealer demands more compensation for warehousing the position.

What this means in practice

A quant desk pricing anything off Treasuries needs to know which layer it is exposed to. A relative-value trader betting on-the-run versus off-the-run is trading a liquidity premium, not credit risk. A repo desk that suddenly cannot find a bond to borrow (it has "gone special") is watching secondary-market demand spill into the financing layer in real time.