VMBIX vs. VTBNX
VMBIX (Vanguard Mortgage-Backed Securities Index Fund Institutional Shares) and VTBNX (Vanguard Total Bond Market II Index Fund) are both Total Bond Market funds from Vanguard. Over the past 10 years, VMBIX returned 1.41%/yr vs 1.55%/yr for VTBNX. Their correlation of 0.87 suggests significant overlap in exposure. VMBIX charges 0.05%/yr vs 0.02%/yr for VTBNX.
Performance
VMBIX vs. VTBNX - Performance Comparison
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Returns By Period
In the year-to-date period, VMBIX achieves a 0.86% return, which is significantly higher than VTBNX's 0.33% return. Over the past 10 years, VMBIX has underperformed VTBNX with an annualized return of 1.41%, while VTBNX has yielded a comparatively higher 1.55% 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%
VTBNX
- 1D
- 0.00%
- 1M
- 0.45%
- YTD
- 0.33%
- 6M
- 0.25%
- 1Y
- 5.21%
- 3Y*
- 4.01%
- 5Y*
- 0.20%
- 10Y*
- 1.55%
VMBIX vs. VTBNX - 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% |
VTBNX Vanguard Total Bond Market II Index Fund | 0.33% | 7.18% | 1.32% | 5.68% | -13.12% | -1.82% | 7.39% | 8.71% | -0.27% | 3.62% |
Correlation
The correlation between VMBIX and VTBNX is 0.90, 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 | 0.90 |
Correlation (3Y) Calculated over the trailing 3-year period | 0.93 |
Correlation (5Y) Calculated over the trailing 5-year period | 0.92 |
Correlation (10Y) Calculated over the trailing 10-year period | 0.87 |
Correlation (All Time) Calculated using the full available price history since Jan 25, 2016 | 0.87 |
The correlation between VMBIX and VTBNX has been stable across timeframes, ranging from 0.87 to 0.93 - a consistent structural relationship.
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Return for Risk
VMBIX vs. VTBNX — Risk / Return Rank
VMBIX
VTBNX
VMBIX vs. VTBNX - 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 Vanguard Total Bond Market II Index Fund (VTBNX). 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 | VTBNX | Difference | |
|---|---|---|---|
| Sharpe ratioReturn per unit of total volatility | +0.52 | ||
| Sortino ratioReturn per unit of downside risk | +0.76 | ||
| Omega ratioGain probability vs. loss probability | 1.34 | 1.23 | +0.11 |
| Calmar ratioReturn relative to maximum drawdown | 2.67 | 1.85 | +0.82 |
| Martin ratioReturn relative to average drawdown | 9.15 | 5.53 | +3.62 |
Data is calculated on a 1-year rolling basis and updated daily. The trend shows the change in the indicator over the past month. | |||
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Sharpe Ratios by Period
| VMBIX | VTBNX | Difference | |
|---|---|---|---|
Sharpe Ratio (1Y)Calculated over the trailing 1-year period | 1.86 | 1.34 | +0.52 |
Sharpe Ratio (5Y)Calculated over the trailing 5-year period | 0.09 | 0.03 | +0.06 |
Sharpe Ratio (10Y)Calculated over the trailing 10-year period | 0.29 | 0.32 | -0.02 |
Sharpe Ratio (All Time)Calculated using the full available price history | 0.51 | 0.38 | +0.14 |
Drawdowns
VMBIX vs. VTBNX - Drawdown Comparison
The maximum VMBIX drawdown since its inception was -17.44%, smaller than the maximum VTBNX drawdown of -18.71%. Use the drawdown chart below to compare losses from any high point for VMBIX and VTBNX.
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Drawdown Indicators
| VMBIX | VTBNX | Difference | |
|---|---|---|---|
Max DrawdownLargest peak-to-trough decline | -17.44% | -18.71% | +1.27% |
Max Drawdown (1Y)Largest decline over 1 year | -2.63% | -2.83% | +0.20% |
Max Drawdown (3Y)Largest decline over 3 years | -7.51% | -5.97% | -1.54% |
Max Drawdown (5Y)Largest decline over 5 years | -17.11% | -18.05% | +0.94% |
Max Drawdown (10Y)Largest decline over 10 years | -17.44% | -18.71% | +1.27% |
Current DrawdownCurrent decline from peak | -1.15% | -2.21% | +1.06% |
Average DrawdownAverage peak-to-trough decline | -2.51% | -4.87% | +2.36% |
Ulcer IndexDepth and duration of drawdowns from previous peaks | 0.77% | 0.95% | -0.18% |
Volatility
VMBIX vs. VTBNX - Volatility Comparison
Vanguard Mortgage-Backed Securities Index Fund Institutional Shares (VMBIX) has a higher volatility of 1.47% compared to Vanguard Total Bond Market II Index Fund (VTBNX) at 1.33%. This indicates that VMBIX's price experiences larger fluctuations and is considered to be riskier than VTBNX based on this measure. The chart below showcases a comparison of their rolling one-month volatility.
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Volatility by Period
| VMBIX | VTBNX | Difference | |
|---|---|---|---|
Volatility (1M)Calculated over the trailing 1-month period | 1.47% | 1.33% | +0.14% |
Volatility (6M)Calculated over the trailing 6-month period | 2.77% | 2.81% | -0.04% |
Volatility (1Y)Calculated over the trailing 1-year period | 3.80% | 3.93% | -0.13% |
Volatility (5Y)Calculated over the trailing 5-year period, annualized | 6.37% | 5.96% | +0.41% |
Volatility (10Y)Calculated over the trailing 10-year period, annualized | 4.79% | 4.93% | -0.14% |
VMBIX vs. VTBNX - Expense Ratio Comparison
VMBIX has a 0.05% expense ratio, which is higher than VTBNX's 0.02% 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. VTBNX - Dividend Comparison
VMBIX's dividend yield for the trailing twelve months is around 4.18%, more than VTBNX's 4.06% yield.
| Position | TTM | 2025 | 2024 | 2023 | 2022 | 2021 | 2020 | 2019 | 2018 | 2017 | 2016 | 2015 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
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% |
VTBNX Vanguard Total Bond Market II Index Fund | 4.06% | 3.95% | 3.77% | 3.13% | 2.54% | 1.82% | 3.12% | 2.79% | 2.56% | 2.52% | 2.55% | 0.00% |
Frequently Asked Questions
With a correlation of 0.90, VMBIX and VTBNX 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 VTBNX (1.33%). In terms of maximum drawdown, VMBIX dropped -17.44% vs VTBNX's -18.71%.
VMBIX currently has the higher Sharpe Ratio (1.86 vs 1.34), 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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