How far back can you test BIL? To Nov 1991, with SHV and VFISX
BIL (T-Bills / Cash) has its own monthly data from Jun 2007. Spliced with SHV and VFISX it reaches back to Nov 1991, which adds 15.6 years (45% of the extended history comes from proxies). Data through Sep 2026.
What you'd have missed
- BIL's own data starts in Jun 2007; SHV and VFISX extend it to Nov 1991, 15.6 more years.
- Its own history misses the 1998 LTCM sell-off and the 2000–02 dot-com bear.
- The extended history's worst drawdown is -2.4% (Jan 1994–Apr 1994), versus -0.4% (Oct 2009–Oct 2015) in the ETF's own years.
- Its worst calendar year, 1994 (-0.6%), predates the ETF.
- SHY is extended with the same VFISX.
How the history is built
BIL (ETF) Jun 2007 → now
SHV (iShares 0-1 Year Treasury Bond ETF) used Feb 2007 → May 2007; its own data runs Feb 2007 → now
VFISX (Vanguard Short-Term Treasury Fund, mutual fund) used Nov 1991 → Jan 2007; its own data runs Nov 1991 → now
Nov 1991Sep 2026
Solid bars are the months each fund contributes to the spliced series; the outline shows how far a proxy's own data runs. Each month uses the youngest fund that has data for it; returns are spliced, not prices (dividends reinvested via adjusted close).
How well each proxy tracked BIL
| Proxy | Kind | Months contributed | Overlap with BIL | Correlation | Tracking error | Tracking difference | Beta | Vol ratio | Grade |
|---|---|---|---|---|---|---|---|---|---|
| SHViShares 0-1 Year Treasury Bond ETF | ETF | Feb 2007–May 20074 months | Jun 2007–Sep 2026232 months | 0.918 | 0.23% | +0.15% | 0.96 | 1.04 | Approximate |
| VFISXVanguard Short-Term Treasury Fund | mutual fund | Nov 1991–Jan 2007183 months | Jun 2007–Sep 2026232 months | 0.256 | 1.76% | +0.54% | 0.83 | 3.25 | Approximate |
| ↳ vs SHV (the link it is spliced onto) | Feb 2007–Sep 2026236 months | 0.437 | 1.64% | +0.37% | 1.34 | 3.07 | |||
Statistics are over the months a proxy and BIL both have data. Tracking error is annualized; tracking difference is the annualized geometric gap (positive: the proxy earned more). Page grade: approximate, the worst grade among the proxies that contribute months.
BIL's own history versus the extended history
| The ETF's own history | Proxy years only | Full extended history | |
|---|---|---|---|
| Window | Jun 2007 – Sep 202619.3 years | Nov 1991 – May 200715.6 years | Nov 1991 – Sep 202634.9 years |
| Growth of $10,000 | $13,061 | $21,995 | $28,728 |
| CAGR | 1.4% | 5.2% | 3.1% |
| Annualized volatility | 0.6% | 2.1% | 1.6% |
| Sharpe ratio (risk-free 0%) | 2.48 | 2.37 | 1.92 |
| Max drawdown | -0.4%Oct 2009 → Oct 2015; recovered Aug 2017 | -2.4%Jan 1994 → Apr 1994; recovered Jan 1995 | -2.4%Jan 1994 → Apr 1994; recovered Jan 1995 |
| Worst complete calendar year | 2015 (-0.1%) | 1994 (-0.6%) | 1994 (-0.6%) |
| Best complete calendar year | 2024 (5.2%) | 1995 (12.1%) | 1995 (12.1%) |
| Longest underwater (months) | 93 | 11 | 93 |
| Major declines covered | 3 | 2 | 5 |
The columns cover different years, so a higher or lower CAGR is not a verdict on the fund; the point is which market regimes each window includes. Growth of $10,000 is the same one-asset, buy-and-hold calculation the live portfolio app makes.
Growth of $10,000
Drawdowns
How BIL did in each major US stock-market decline since 1985
| Decline | S&P 500 | BIL over the same months | Source of those months |
|---|---|---|---|
| 1987 crashSep 1987–Nov 1987 | -29.8% | not covered | before available data |
| 1998 LTCM sell-offJul 1998–Aug 1998 | -15.3% | 2.0% | VFISX |
| 2000–02 dot-com bearSep 2000–Sep 2002 | -44.7% | 20.3% | VFISX |
| 2007–09 financial crisisNov 2007–Feb 2009 | -50.8% | 2.4% | ETF |
| 2020 COVID crashJan 2020–Mar 2020 | -19.4% | 0.4% | ETF |
| 2022 inflation bearJan 2022–Sep 2022 | -23.9% | 0.6% | ETF |
The decline windows are computed, not chosen: every peak-to-trough fall of at least 15% (month-end) in the S&P 500 series since 1985. The fund's figure compounds its monthly returns from the month after the S&P 500's peak through the trough.
BIL's own five deepest drawdowns (extended history)
| Peak | Trough | Depth | Recovery | Source of the decline months |
|---|---|---|---|---|
| Jan 1994 | Apr 1994 | -2.4% | Jan 1995 | VFISX |
| Sep 1992 | Nov 1992 | -1.6% | Jan 1993 | VFISX |
| Mar 2004 | May 2004 | -1.4% | Oct 2004 | VFISX |
| Jan 1996 | Apr 1996 | -1.1% | Jul 1996 | VFISX |
| Oct 2001 | Dec 2001 | -1.1% | Feb 2002 | VFISX |
This covers declines the equity windows miss, such as the bond bear markets of 1994 and 2022.
Caveats
- SHV is a different ETF with a similar mandate. The measured gap to BIL while both existed is +0.15% a year.
- Before Feb 2007 the returns are VFISX's, after that fund's own costs; the measured gap while both existed is +0.54% a year.
- The ultra-short Treasury proxy is a 1-3 year Treasury fund, not Treasury bills, so before 2007 the cash series carries some duration that T-bills do not.
- Monthly month-end data: intra-month drawdowns were deeper than shown.
- Dividends are reinvested; no taxes or trading costs are modeled.
- Our data source's series for VFISX begins Nov 1991; the fund itself may be older.
Test it yourself
Open BIL as a one-asset portfolio in the live app, where every number recomputes from fresh data.
Open BIL (100%) in the portfolio builder →Used in portfolios: Permanent Portfolio, Betterment Core, Buffett 90/10
Used in guides: Betterment Core, Buffett 90/10, Permanent
Frequently asked questions
- How far back does BIL data go?
- BIL (T-Bills / Cash) has its own monthly data from Jun 2007. Spliced with SHV and VFISX it reaches back to Nov 1991, which adds 15.6 years (45% of the extended history comes from proxies). Data through Sep 2026.
- What did BIL do before 2007?
- Before Jun 2007 the series is SHV and VFISX's. Those 15.6 years (Nov 1991–May 2007) show 5.2% a year with 2.1% annualized volatility and a worst drawdown of -2.4% (Jan 1994–Apr 1994). In major S&P 500 declines: 1998 LTCM sell-off, 2.0% versus -15.3% for the S&P 500 (VFISX); 2000–02 dot-com bear, 20.3% versus -44.7% for the S&P 500 (VFISX). The full extended history's worst drawdown is -2.4% (Jan 1994–Apr 1994).
- How closely does SHV track BIL?
- Over 232 overlapping months (Jun 2007–Sep 2026), SHV had a correlation of 0.918 with BIL, a tracking error of 0.2% a year and a tracking difference of +0.15% a year (grade: approximate). Over 232 overlapping months (Jun 2007–Sep 2026), VFISX had a correlation of 0.256 with BIL, a tracking error of 1.8% a year and a tracking difference of +0.54% a year (grade: approximate).
Methodology
- Source
- Yahoo Finance via MarketHeist, monthly adjusted close (dividends reinvested). Months run to the last complete calendar month.
- Splice rule
- Each month uses the youngest fund that has data for it; returns are spliced, not prices (dividends reinvested via adjusted close).
- Numbers
- Computed by the MarketHeist portfolio engine as a one-asset, 100% buy-and-hold portfolio, the same calculation the live app makes. Sharpe uses a risk-free rate of 0%. Drawdowns are month-end.
- Correlation
- Pearson correlation of monthly returns over the months both funds have.
- Tracking error
- Standard deviation of the monthly return differences (proxy minus BIL) times the square root of 12.
- Tracking difference
- Annualized geometric return of the proxy minus that of BIL over the overlap. Positive means the proxy earned more.
- Beta and vol ratio
- Beta is the covariance of the proxy with BIL divided by the variance of BIL; vol ratio is the proxy's standard deviation divided by BIL's.
- Grades
- Close: correlation of at least 0.95 and tracking error of at most 3%. Approximate: tracking error of at most 8% and either a cash-like fund (volatility of at most 3%) or correlation of at least 0.80 with a vol ratio of at most 1.25. Category stand-in: anything weaker.
- Generated
- 2026-10-10; data through Sep 2026. Reproduce hash of the full extended one-asset portfolio:
32799c055128c234
Historical simulation, not investment advice. Past returns, including spliced proxy returns, do not predict future results.