WFBIX vs. SSAFX
WFBIX (iShares U.S. Aggregate Bond Index Fund) and SSAFX (State Street Aggregate Bond Index Portfolio) are both Intermediate Core Bond funds. Over the past 10 years, WFBIX returned 1.94%/yr vs 27.80%/yr for SSAFX. With a 0.95 correlation, they move nearly in lockstep. WFBIX charges 0.05%/yr vs 0.02%/yr for SSAFX.
Performance
WFBIX vs. SSAFX - Performance Comparison
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Returns By Period
The year-to-date returns for both investments are quite close, with WFBIX having a 0.21% return and SSAFX slightly higher at 0.22%. Over the past 10 years, WFBIX has underperformed SSAFX with an annualized return of 1.94%, while SSAFX has yielded a comparatively higher 27.80% annualized return.
WFBIX
- 1D
- -0.22%
- 1M
- 0.11%
- YTD
- 0.21%
- 6M
- 0.32%
- 1Y
- 4.53%
- 3Y*
- 5.26%
- 5Y*
- 0.87%
- 10Y*
- 1.94%
SSAFX
- 1D
- -0.20%
- 1M
- 0.09%
- YTD
- 0.22%
- 6M
- 0.32%
- 1Y
- 4.55%
- 3Y*
- 3.83%
- 5Y*
- -0.03%
- 10Y*
- 27.80%
WFBIX vs. SSAFX - Yearly Performance Comparison
| 2026 (YTD) | 2025 | 2024 | 2023 | 2022 | 2021 | 2020 | 2019 | 2018 | 2017 | |
|---|---|---|---|---|---|---|---|---|---|---|
WFBIX iShares U.S. Aggregate Bond Index Fund | 0.21% | 7.16% | 1.43% | 9.65% | -13.03% | -1.79% | 7.40% | 8.72% | -0.08% | 3.39% |
SSAFX State Street Aggregate Bond Index Portfolio | 0.22% | 6.81% | 1.34% | 5.61% | -13.30% | -1.72% | 978.57% | 8.69% | -0.12% | 3.38% |
Correlation
The correlation between WFBIX and SSAFX is 0.93, 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 | 0.93 |
Correlation (3Y) Calculated over the trailing 3-year period | 0.95 |
Correlation (5Y) Calculated over the trailing 5-year period | 0.97 |
Correlation (10Y) Calculated over the trailing 10-year period | 0.96 |
Correlation (All Time) Calculated using the full available price history since Sep 23, 2014 | 0.95 |
The correlation between WFBIX and SSAFX has been stable across timeframes, ranging from 0.93 to 0.97 - a consistent structural relationship.
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Return for Risk
WFBIX vs. SSAFX — Risk / Return Rank
WFBIX
SSAFX
WFBIX vs. SSAFX - Risk-Adjusted Trends Comparison
This table presents a comparison of risk-adjusted performance metrics for iShares U.S. Aggregate Bond Index Fund (WFBIX) and State Street Aggregate Bond Index Portfolio (SSAFX). 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.
| WFBIX | SSAFX | Difference | |
|---|---|---|---|
| Sharpe ratioReturn per unit of total volatility | -0.10 | ||
| Sortino ratioReturn per unit of downside risk | -0.14 | ||
| Omega ratioGain probability vs. loss probability | 1.23 | 1.25 | -0.01 |
| Calmar ratioReturn relative to maximum drawdown | 1.70 | 1.89 | -0.19 |
| Martin ratioReturn relative to average drawdown | 5.08 | 5.75 | -0.68 |
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
| WFBIX | SSAFX | Difference | |
|---|---|---|---|
Sharpe Ratio (1Y)Calculated over the trailing 1-year period | 1.30 | 1.39 | -0.10 |
Sharpe Ratio (5Y)Calculated over the trailing 5-year period | 0.14 | -0.01 | +0.14 |
Sharpe Ratio (10Y)Calculated over the trailing 10-year period | 0.38 | 0.10 | +0.28 |
Sharpe Ratio (All Time)Calculated using the full available price history | 0.94 | 0.09 | +0.85 |
Drawdowns
WFBIX vs. SSAFX - Drawdown Comparison
The maximum WFBIX drawdown since its inception was -18.68%, roughly equal to the maximum SSAFX drawdown of -18.74%. Use the drawdown chart below to compare losses from any high point for WFBIX and SSAFX.
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Drawdown Indicators
| WFBIX | SSAFX | Difference | |
|---|---|---|---|
Max DrawdownLargest peak-to-trough decline | -18.68% | -18.74% | +0.06% |
Max Drawdown (1Y)Largest decline over 1 year | -3.02% | -2.74% | -0.28% |
Max Drawdown (3Y)Largest decline over 3 years | -6.09% | -6.09% | 0.00% |
Max Drawdown (5Y)Largest decline over 5 years | -17.84% | -18.10% | +0.26% |
Max Drawdown (10Y)Largest decline over 10 years | -18.68% | -18.74% | +0.06% |
Current DrawdownCurrent decline from peak | -1.71% | -2.81% | +1.10% |
Average DrawdownAverage peak-to-trough decline | -2.26% | -4.41% | +2.15% |
Ulcer IndexDepth and duration of drawdowns from previous peaks | 1.01% | 0.90% | +0.11% |
Volatility
WFBIX vs. SSAFX - Volatility Comparison
iShares U.S. Aggregate Bond Index Fund (WFBIX) and State Street Aggregate Bond Index Portfolio (SSAFX) have volatilities of 1.31% and 1.26%, 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.
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Volatility by Period
| WFBIX | SSAFX | Difference | |
|---|---|---|---|
Volatility (1M)Calculated over the trailing 1-month period | 1.31% | 1.26% | +0.05% |
Volatility (6M)Calculated over the trailing 6-month period | 2.80% | 2.63% | +0.17% |
Volatility (1Y)Calculated over the trailing 1-year period | 3.97% | 3.74% | +0.23% |
Volatility (5Y)Calculated over the trailing 5-year period, annualized | 6.40% | 5.95% | +0.45% |
Volatility (10Y)Calculated over the trailing 10-year period, annualized | 5.17% | 277.46% | -272.29% |
WFBIX vs. SSAFX - Expense Ratio Comparison
WFBIX has a 0.05% expense ratio, which is higher than SSAFX'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
WFBIX vs. SSAFX - Dividend Comparison
WFBIX's dividend yield for the trailing twelve months is around 3.91%, less than SSAFX's 4.17% yield.
| Position | TTM | 2025 | 2024 | 2023 | 2022 | 2021 | 2020 | 2019 | 2018 | 2017 | 2016 | 2015 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
SSAFX State Street Aggregate Bond Index Portfolio | 4.17% | 3.70% | 3.76% | 3.16% | 2.49% | 1.90% | 2.41% | 2.88% | 2.82% | 2.42% | 2.21% | 3.21% |
WFBIX iShares U.S. Aggregate Bond Index Fund | 3.91% | 3.78% | 3.68% | 6.82% | 2.60% | 2.04% | 2.43% | 2.88% | 2.71% | 2.24% | 2.25% | 2.20% |
Frequently Asked Questions
With a correlation of 0.93, WFBIX and SSAFX 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.
WFBIX has higher volatility (1.31%) compared to SSAFX (1.26%). In terms of maximum drawdown, WFBIX dropped -18.68% vs SSAFX's -18.74%.
SSAFX currently has the higher Sharpe Ratio (1.39 vs 1.30), 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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