These levels are back-tested. Every one was computed after the fact by applying the rules to historical data, which benefits from hindsight in the choice of rules and is not a record of trading. An index cannot be invested in directly. Methodology v1.0 takes effect at the September 30, 2026 rebalance.
Level since the base date
215 monthly rebalances, chained from 100 at September 30, 2008. The y axis is an index level, not a rate. The base is the month-end before the first published level, so the first point after it already carries a month of return.
Total return
Cumulative and annualized total return over trailing periods to August 31, 2026.
Period
Cumulative
Annualized
1 month
+0.32%
–
3 months
+0.96%
–
1 year
+3.89%
+3.89%
3 years
+14.65%
+4.66%
5 years
+20.23%
+3.75%
10 years
+27.05%
+2.42%
Since inception
+28.01%
1.39%
Periods under one year are not annualized, and the dash in that column is a refusal rather than a gap: restating one month as a yearly rate extrapolates a single month's movement across twelve, which overstates gains and losses alike.
Calendar year returns
Total return by calendar year since inception.
Year
Total return
20268 months
+2.46%
2025
+4.31%
2024
+5.38%
2023
+5.13%
2022
+1.53%
2021
+0.05%
2020
+0.56%
2019
+2.22%
2018
+1.84%
2017
+0.82%
2016
+0.25%
2015
+0.03%
2014
+0.03%
2013
+0.05%
2012
+0.08%
2011
+0.07%
2010
+0.13%
2009
+0.14%
20083 months
+0.06%
Market value weighted, rebalanced monthly on the last trading day. Amount outstanding is what was auctioned, less par Treasury has bought back and retired, less what the Federal Reserve holds, a bond the Fed owns is outstanding but not investable, so deducting it is what makes the weights describe a portfolio somebody could actually hold. Levels are month-end figures, so this sits behind the daily prices elsewhere on this site by design.
Largest holdings
17 at the August 31, 2026 rebalance
The 5 heaviest, by weight. Each security's return is its own total return over the month; its contribution is that return times its weight, and every holding's contribution adds to the index return above.
The 5 heaviest holdings of 1-3 Month Bill at the August 31, 2026 rebalance, with each one's weight, total return over the month and contribution to the index return.
Check this level yourself. Every holding is published each month with the three deductions that set its weight, both prices, and its contribution, and the contributions add to the return above. See the constituents.
Index levels before September 30, 2026 are back-tested. They were computed after the fact by applying the rules to historical data, which benefits from hindsight in the choice of rules, and an index cannot be invested in directly. Methodology v1.0 takes effect at that rebalance, when levels begin to be struck on the day; the rulebook is identical either way, and the version is published on every row.
A fitted curve is a fit, not a quote. Daily error averages 3.8 basis points across the history and reaches about 20 on the worst days, in December 2008, when the market was genuinely hard to fit one smooth curve to. Every curve page publishes its own fit error rather than burying it.
Safe Rate™, Safe Rate Indices™ and the Safe Rate US Treasury Index™ are trademarks of Safe Rate, claimed through use in commerce and not registered. Third-party marks are the property of their owners, which are not affiliated with and do not endorse this data.
Curves are fitted from public Treasury data and carry fit error; figures are not a record of trading, and an index cannot be invested in directly. No claim of compliance with the IOSCO Principles for Financial Benchmarks is made or implied. Not investment advice, not an offer, and not a recommendation to buy or sell any security.