VMBIX vs. FXNAX
VMBIX (Vanguard Mortgage-Backed Securities Index Fund Institutional Shares) and FXNAX (Fidelity U.S. Bond Index Fund) are both Total Bond Market funds. Over the past 10 years, VMBIX returned 1.41%/yr vs 1.51%/yr for FXNAX. Their correlation of 0.87 suggests significant overlap in exposure. VMBIX charges 0.05%/yr vs 0.03%/yr for FXNAX.
Performance
VMBIX vs. FXNAX - Performance Comparison
Loading charts...
Returns By Period
In the year-to-date period, VMBIX achieves a 0.86% return, which is significantly higher than FXNAX's 0.40% return. Over the past 10 years, VMBIX has underperformed FXNAX with an annualized return of 1.41%, while FXNAX has yielded a comparatively higher 1.51% annualized return.
VMBIX
- 1D
- 0.04%
- 1M
- 0.47%
- YTD
- 0.86%
- 6M
- 1.01%
- 1Y
- 7.00%
- 3Y*
- 4.71%
- 5Y*
- 0.57%
- 10Y*
- 1.41%
FXNAX
- 1D
- 0.00%
- 1M
- 0.51%
- YTD
- 0.40%
- 6M
- 0.34%
- 1Y
- 5.37%
- 3Y*
- 4.02%
- 5Y*
- 0.12%
- 10Y*
- 1.51%
VMBIX vs. FXNAX - Yearly Performance Comparison
| 2026 (YTD) | 2025 | 2024 | 2023 | 2022 | 2021 | 2020 | 2019 | 2018 | 2017 | |
|---|---|---|---|---|---|---|---|---|---|---|
VMBIX Vanguard Mortgage-Backed Securities Index Fund Institutional Shares | 0.86% | 8.44% | 1.78% | 4.97% | -11.56% | -1.30% | 3.77% | 6.19% | 0.88% | 2.38% |
FXNAX Fidelity U.S. Bond Index Fund | 0.40% | 7.14% | 1.35% | 5.82% | -13.55% | -2.10% | 7.63% | 8.50% | 0.04% | 3.50% |
Correlation
The correlation between VMBIX and FXNAX is 0.92, indicating a strong positive relationship between their price movements. Combining them offers limited diversification - they tend to fall together during downturns.
| Correlation | |
|---|---|
Correlation (1Y) Calculated over the trailing 1-year period | 0.92 |
Correlation (3Y) Calculated over the trailing 3-year period | 0.93 |
Correlation (5Y) Calculated over the trailing 5-year period | 0.93 |
Correlation (10Y) Calculated over the trailing 10-year period | 0.88 |
Correlation (All Time) Calculated using the full available price history since May 5, 2011 | 0.87 |
The correlation between VMBIX and FXNAX has been stable across timeframes, ranging from 0.87 to 0.93 - a consistent structural relationship.
Compare stocks, funds, or ETFs
Search for stocks, ETFs, and funds for a quick comparison or use the comparison tool for more options.
Return for Risk
VMBIX vs. FXNAX — Risk / Return Rank
VMBIX
FXNAX
VMBIX vs. FXNAX - Risk-Adjusted Trends Comparison
This table presents a comparison of risk-adjusted performance metrics for Vanguard Mortgage-Backed Securities Index Fund Institutional Shares (VMBIX) and Fidelity U.S. Bond Index Fund (FXNAX). 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.
| VMBIX | FXNAX | Difference | |
|---|---|---|---|
| Sharpe ratioReturn per unit of total volatility | +0.50 | ||
| Sortino ratioReturn per unit of downside risk | +0.73 | ||
| Omega ratioGain probability vs. loss probability | 1.34 | 1.24 | +0.10 |
| Calmar ratioReturn relative to maximum drawdown | 2.67 | 1.83 | +0.84 |
| Martin ratioReturn relative to average drawdown | 9.15 | 5.61 | +3.55 |
Data is calculated on a 1-year rolling basis and updated daily. The trend shows the change in the indicator over the past month. | |||
Loading charts...
Sharpe Ratios by Period
| VMBIX | FXNAX | Difference | |
|---|---|---|---|
Sharpe Ratio (1Y)Calculated over the trailing 1-year period | 1.86 | 1.36 | +0.50 |
Sharpe Ratio (5Y)Calculated over the trailing 5-year period | 0.09 | 0.02 | +0.07 |
Sharpe Ratio (10Y)Calculated over the trailing 10-year period | 0.29 | 0.30 | -0.01 |
Sharpe Ratio (All Time)Calculated using the full available price history | 0.51 | 0.45 | +0.06 |
Drawdowns
VMBIX vs. FXNAX - Drawdown Comparison
The maximum VMBIX drawdown since its inception was -17.44%, smaller than the maximum FXNAX drawdown of -19.51%. Use the drawdown chart below to compare losses from any high point for VMBIX and FXNAX.
Loading charts...
Drawdown Indicators
| VMBIX | FXNAX | Difference | |
|---|---|---|---|
Max DrawdownLargest peak-to-trough decline | -17.44% | -19.51% | +2.07% |
Max Drawdown (1Y)Largest decline over 1 year | -2.63% | -2.94% | +0.31% |
Max Drawdown (3Y)Largest decline over 3 years | -7.51% | -6.16% | -1.35% |
Max Drawdown (5Y)Largest decline over 5 years | -17.11% | -18.54% | +1.43% |
Max Drawdown (10Y)Largest decline over 10 years | -17.44% | -19.51% | +2.07% |
Current DrawdownCurrent decline from peak | -1.15% | -2.89% | +1.74% |
Average DrawdownAverage peak-to-trough decline | -2.51% | -3.87% | +1.36% |
Ulcer IndexDepth and duration of drawdowns from previous peaks | 0.77% | 0.96% | -0.19% |
Volatility
VMBIX vs. FXNAX - Volatility Comparison
Vanguard Mortgage-Backed Securities Index Fund Institutional Shares (VMBIX) and Fidelity U.S. Bond Index Fund (FXNAX) have volatilities of 1.47% and 1.41%, respectively, indicating that both stocks experience similar levels of price fluctuations. This suggests that the risk associated with both stocks, as measured by volatility, is nearly the same. The chart below showcases a comparison of their rolling one-month volatility.
Loading charts...
Volatility by Period
| VMBIX | FXNAX | Difference | |
|---|---|---|---|
Volatility (1M)Calculated over the trailing 1-month period | 1.47% | 1.41% | +0.06% |
Volatility (6M)Calculated over the trailing 6-month period | 2.77% | 2.82% | -0.05% |
Volatility (1Y)Calculated over the trailing 1-year period | 3.80% | 3.97% | -0.17% |
Volatility (5Y)Calculated over the trailing 5-year period, annualized | 6.37% | 6.07% | +0.30% |
Volatility (10Y)Calculated over the trailing 10-year period, annualized | 4.79% | 5.01% | -0.22% |
VMBIX vs. FXNAX - Expense Ratio Comparison
VMBIX has a 0.05% expense ratio, which is higher than FXNAX's 0.03% expense ratio. However, both funds are considered low-cost compared to the broader market, where average expense ratios usually range from 0.3% to 0.9%.
Dividends
VMBIX vs. FXNAX - Dividend Comparison
VMBIX's dividend yield for the trailing twelve months is around 4.18%, more than FXNAX's 3.71% yield.
| Position | TTM | 2025 | 2024 | 2023 | 2022 | 2021 | 2020 | 2019 | 2018 | 2017 | 2016 | 2015 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
FXNAX Fidelity U.S. Bond Index Fund | 3.71% | 3.58% | 3.40% | 3.15% | 1.81% | 1.74% | 2.92% | 2.68% | 2.74% | 2.57% | 2.76% | 2.52% |
VMBIX Vanguard Mortgage-Backed Securities Index Fund Institutional Shares | 4.18% | 4.20% | 4.27% | 3.29% | 2.33% | 1.01% | 2.02% | 2.76% | 2.74% | 2.18% | 2.13% | 2.04% |
Frequently Asked Questions
With a correlation of 0.92, VMBIX and FXNAX 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.
VMBIX has higher volatility (1.47%) compared to FXNAX (1.41%). In terms of maximum drawdown, VMBIX dropped -17.44% vs FXNAX's -19.51%.
VMBIX currently has the higher Sharpe Ratio (1.86 vs 1.36), 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.
Find the right allocation for VMBIX and FXNAX
Add both to a portfolio and optimize allocations for your target — whether that's maximizing returns, minimizing drawdowns, or balancing risk across holdings.
Open Portfolio Optimizer