Methodology

Text on this page was drafted with AI tools; every figure is computed by code from the cited official source.

Every number on 500metrics is our own calculation from official U.S. Treasury data, published by code with the dates shown; this page explains each one.

How a number reaches a page

1. Collected from the official source. Our code fetches each dataset from its publisher (listed at Sources ) at the publisher's release times, politely and within its terms. Every file we receive is archived unchanged, so any number can be rebuilt from the original.
2. Calculated by code. Each measure is computed by a fixed, versioned program from the archived data. No person types, edits or rounds a number by hand.
3. Checked against official totals. Before a reading goes live, it is reconciled with the government's own published totals where one exists (for example, the room under the debt limit with the Daily Treasury Statement). A reading that fails is held back, the page keeps its last good reading with that reading's date, and the failure is investigated.
4. Published with its dates and source. Each number shows three times: when the event happened, when the source published it, and when we last checked the source. A page never shows a date newer than its data.

Conventions

• Times. Auction times are US Eastern Time, as Treasury states them. Our check times are UTC.
• Units. Amounts are in US dollars and say their scale in words ("trillion", "billion", "million"). Yields and rates are percentages as published by the source, with the number of decimals the source uses.
• Revisions. Sources sometimes revise figures. We store every change rather than overwriting it; when a revision changes a number on a page, the page shows the new value and the date it changed.
• Late data. If a source misses its usual release time, the page keeps its previous reading and says it is late. Federal holidays are not counted as late.
• Comparisons with history. Statements such as "lowest since" or a percentile always name their window and their series (for example, "since 7 April 2008, the first auction with bidder amounts"). They compare a figure only with earlier values of the same series.
• What a number cannot tell. Every data page has a box headed "What this number cannot tell you", which lists the limits of the measure next to the number, not in a footnote.
• Scenarios. Where a page shows a figure under stated assumptions, it is labelled "a scenario, not a prediction", lists every assumption and shows the range it was run over.
• Estimates by others. Outside estimates, such as when the Treasury could exhaust its room under the debt limit, appear in their own box with their author and publication date. 500metrics publishes no estimate of that date.
• Words. Pages state facts, counts, dates and formulas. They do not describe a security as cheap or dear, forecast prices or yields, or suggest any trade.

Measures

Each measure has its own section with its definition, formula, source fields, units, the window it is compared over, known traps in the source data and what it cannot tell. The full section is published here when the measure's page goes live. The numbered list of all measures is at Metrics.

Auction results

For each Treasury note and bond auction: the high yield, the bid-to-cover ratio (the amount bid divided by the amount accepted), and the shares of the accepted amount taken by indirect bidders, direct bidders and primary dealers, as Treasury reports them. Each auction is compared with earlier auctions of the same security type and term: with the previous auction of that term, over the last 12 auctions, and over the whole series (bidder shares exist from 7 April 2008). Bill auctions are shown with their high rate and bid-to-cover ratio. These comparisons describe how much demand an auction drew compared with its own history; they say nothing about the value of the security.

Room under the debt limit

The statutory debt limit minus total debt subject to the limit, as reported in Table IIIC of the Daily Treasury Statement, with Treasury's cash balance shown beside it. While the limit is suspended, the page says so and shows debt subject to the limit without a room figure. Category names in Table IIIC changed in 2022; the section lists how older days are mapped.

Debt coming due

Marketable Treasury securities outstanding at each month end, from the Monthly Statement of the Public Debt, grouped by the month they mature. Each month-end view is kept, so the calendar can be shown as it stood on any month end since January 2001. The share owned by the Federal Reserve is shown from the New York Fed's published holdings.

Interest cost

Gross interest expense on the public debt for the fiscal year to date, from Fiscal Data. It is a different measure from net interest outlays in the Monthly Treasury Statement, which subtracts the interest credited to the government's own trust funds and other interest the government receives. Both are named on the page and never swapped.

Yield curve and bill rates

Treasury's daily par yield curve (nominal), its par real yield curve (from TIPS) and its daily bill rates, each as Treasury publishes it for the day, with no smoothing or interpolation of ours. Treasury builds the par curves from market quotes it collects late each afternoon, so they describe where Treasury securities traded that day, not any one auction. Bill rates are shown on both bases Treasury gives: the discount rate and the investment (coupon-equivalent) rate. The changes and the 10-year minus 2-year spread are ours, in basis points: the latest day against the curve's previous day, and against the same day a year earlier (or the business day before it when that day has no curve). A 52-week high or low names the day it was set; on a tie it is the latest such day. A term that leaves the published curve sends readers on to the curve page.

Reference rates

The overnight reference rates the Federal Reserve Bank of New York publishes each business day: the Secured Overnight Financing Rate (SOFR), the Tri-Party General Collateral Rate (TGCR), the Broad General Collateral Rate (BGCR), the effective federal funds rate (EFFR) and the Overnight Bank Funding Rate (OBFR). Each is shown as published for its business day, with the percentiles and volume the New York Fed gives and, for EFFR, the Federal Open Market Committee's target range on that day. The New York Fed can revise a day after first publishing it; the page shows the current value, marks the day as revised and lists the first and current values. The day-to-day change is ours, in basis points.

Corrections

When a number on the site was wrong, the page shows the corrected value with a dated "Corrected" note linking to Corrections, where every correction is logged.

Method changelog