FIBUX vs. FNDSX
FIBUX (Fidelity Flex U.S. Bond Index Fund) and FNDSX (Fidelity Sustainability Bond Index Fund) are both Total Bond Market funds from Fidelity. Over the past 5 years, FIBUX returned -0.09%/yr vs -0.14%/yr for FNDSX. With a 0.97 correlation, they move nearly in lockstep. FIBUX charges 0.00%/yr vs 0.10%/yr for FNDSX.
Performance
FIBUX vs. FNDSX - Performance Comparison
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Returns By Period
In the year-to-date period, FIBUX achieves a 0.13% return, which is significantly higher than FNDSX's 0.10% return.
FIBUX
- 1D
- -0.33%
- 1M
- 0.57%
- YTD
- 0.13%
- 6M
- 0.47%
- 1Y
- 4.25%
- 3Y*
- 3.89%
- 5Y*
- -0.09%
- 10Y*
- —
FNDSX
- 1D
- -0.32%
- 1M
- 0.55%
- YTD
- 0.10%
- 6M
- 0.42%
- 1Y
- 4.12%
- 3Y*
- 3.80%
- 5Y*
- -0.14%
- 10Y*
- —
FIBUX vs. FNDSX - Yearly Performance Comparison
| 2026 (YTD) | 2025 | 2024 | 2023 | 2022 | 2021 | 2020 | 2019 | 2018 | |
|---|---|---|---|---|---|---|---|---|---|
FIBUX Fidelity Flex U.S. Bond Index Fund | 0.13% | 7.20% | 1.31% | 5.46% | -13.41% | -2.16% | 7.08% | 8.58% | 2.17% |
FNDSX Fidelity Sustainability Bond Index Fund | 0.10% | 7.03% | 1.23% | 5.44% | -13.34% | -2.22% | 6.95% | 8.30% | 1.89% |
Correlation
The correlation between FIBUX and FNDSX is 0.97 - these two move nearly in lockstep. At this level, holding both provides almost no diversification benefit. If you already own one, adding the other does little to reduce portfolio risk.
| Correlation | |
|---|---|
Correlation (1Y) Calculated over the trailing 1-year period | 0.97 |
Correlation (3Y) Calculated over the trailing 3-year period | 0.97 |
Correlation (5Y) Calculated over the trailing 5-year period | 0.98 |
Correlation (All Time) Calculated using the full available price history since Jun 19, 2018 | 0.97 |
The correlation between FIBUX and FNDSX has been stable across timeframes, ranging from 0.97 to 0.98 - a consistent structural relationship.
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Return for Risk
FIBUX vs. FNDSX — Risk / Return Rank
FIBUX
FNDSX
FIBUX vs. FNDSX - Risk-Adjusted Trends Comparison
This table presents a comparison of risk-adjusted performance metrics for Fidelity Flex U.S. Bond Index Fund (FIBUX) and Fidelity Sustainability Bond Index Fund (FNDSX). Risk-adjusted metrics are performance indicators that assess an investment's returns in relation to its risk, enabling a more accurate comparison of different investment options.
Values are calculated on a 1-year rolling basis and updated daily. Risk-adjusted metrics are more stable over longer periods — use the period switch above to explore them.
| FIBUX | FNDSX | Difference | |
|---|---|---|---|
| Sharpe ratioReturn per unit of total volatility | +0.03 | ||
| Sortino ratioReturn per unit of downside risk | +0.02 | ||
| Omega ratioGain probability vs. loss probability | 1.20 | 1.20 | +0.01 |
| Calmar ratioReturn relative to maximum drawdown | 1.52 | 1.48 | +0.03 |
| Martin ratioReturn relative to average drawdown | 4.23 | 4.17 | +0.06 |
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Drawdowns
FIBUX vs. FNDSX - Drawdown Comparison
The maximum FIBUX drawdown since its inception was -19.76%, roughly equal to the maximum FNDSX drawdown of -19.72%. Use the drawdown chart below to compare losses from any high point for FIBUX and FNDSX.
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Drawdown Indicators
| FIBUX | FNDSX | Difference | |
|---|---|---|---|
Max DrawdownLargest peak-to-trough decline | -19.76% | -19.72% | -0.04% |
Max Drawdown (1Y)Largest decline over 1 year | -2.97% | -2.94% | -0.03% |
Max Drawdown (3Y)Largest decline over 3 years | -6.09% | -6.11% | +0.02% |
Max Drawdown (5Y)Largest decline over 5 years | -18.40% | -18.30% | -0.10% |
Current DrawdownCurrent decline from peak | -3.75% | -4.06% | +0.31% |
Average DrawdownAverage peak-to-trough decline | -5.78% | -6.48% | +0.70% |
Ulcer IndexDepth and duration of drawdowns from previous peaks | 1.06% | 1.04% | +0.02% |
Volatility
FIBUX vs. FNDSX - Volatility Comparison
The current volatility for Fidelity Flex U.S. Bond Index Fund (FIBUX) is 1.11%, while Fidelity Sustainability Bond Index Fund (FNDSX) has a volatility of 1.20%. This indicates that FIBUX experiences smaller price fluctuations and is considered to be less risky than FNDSX based on this measure. The chart below showcases a comparison of their rolling one-month volatility.
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Volatility by Period
| FIBUX | FNDSX | Difference | |
|---|---|---|---|
Volatility (1M)Calculated over the trailing 1-month period | 1.11% | 1.20% | -0.09% |
Volatility (6M)Calculated over the trailing 6-month period | 2.90% | 2.89% | +0.01% |
Volatility (1Y)Calculated over the trailing 1-year period | 3.97% | 3.92% | +0.05% |
Volatility (5Y)Calculated over the trailing 5-year period, annualized | 6.04% | 6.01% | +0.03% |
Volatility (10Y)Calculated over the trailing 10-year period, annualized | 5.11% | 5.30% | -0.19% |
FIBUX vs. FNDSX - Expense Ratio Comparison
FIBUX has a 0.00% expense ratio, which is lower than FNDSX's 0.10% expense ratio. Despite the difference, both funds are considered low-cost compared to the broader market, where average expense ratios usually range from 0.3% to 0.9%.
Dividends
FIBUX vs. FNDSX - Dividend Comparison
FIBUX's dividend yield for the trailing twelve months is around 4.09%, more than FNDSX's 3.97% yield.
| Position | TTM | 2025 | 2024 | 2023 | 2022 | 2021 | 2020 | 2019 | 2018 | 2017 |
|---|---|---|---|---|---|---|---|---|---|---|
FIBUX Fidelity Flex U.S. Bond Index Fund | 4.09% | 3.95% | 3.65% | 2.93% | 1.62% | 1.18% | 2.32% | 2.96% | 2.70% | 2.45% |
FNDSX Fidelity Sustainability Bond Index Fund | 3.97% | 3.84% | 3.53% | 2.84% | 1.55% | 1.17% | 1.79% | 3.17% | 1.56% | 0.00% |
Frequently Asked Questions
With a correlation of 0.97, FIBUX and FNDSX move almost identically. Holding both adds very little diversification - you're essentially doubling your position in the same market segment. Choosing one is usually more capital-efficient.
FNDSX has higher volatility (1.20%) compared to FIBUX (1.11%). In terms of maximum drawdown, FIBUX dropped -19.76% vs FNDSX's -19.72%.
FIBUX currently has the higher Sharpe Ratio (1.14 vs 1.11), meaning it's delivered slightly more return per unit of risk over the trailing 12 months. However, this ranking shifts over time - use the Risk/Return Score above for a more comprehensive view that combines Sharpe, Sortino, and other measures used by quantitative funds.
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