The face-value-weighted average remaining maturity of marketable Treasury debt. In one line: a shorter WAM means the Treasury reprices faster with rates and rolls its debt more often; a longer WAM means the duration risk has been shifted onto the market instead.
This graph shows the weighted average maturity of outstanding Treasury securities. Non-marketable securities and instruments of marginal size are excluded. Each series is the average of individual securities weighted by outstanding face value.
Why it matters: WAM is the outcome of the Treasury's choice between retaining rate risk and pushing duration onto the market. In the zero-rate years the Treasury termed out cheaply — WAM lengthened through the 2010s and approached record highs after 2020; when deficits widen and the Treasury wants to spare the long end, bill-heavy issuance drags WAM back down, at the cost of faster pass-through of policy rates into interest expense (see the average interest rate page). For the bond market, WAM together with the instrument mix defines how much debt must be repriced by the market each year. Keep magnitude and speed distinct: the level of rates sets how large the interest bill ultimately gets, while WAM sets how fast it gets there — the 2022 hiking cycle showed up in interest outlays as quickly as it did because of the bill-heavy, short-repricing structure of the debt at the time.