SSFEX vs. FXNAX

Last updated Jun 5, 2026

SSFEX (State Street Aggregate Bond Index Fund Class K) and FXNAX (Fidelity U.S. Bond Index Fund) are both Total Bond Market funds. Over the past 10 years, SSFEX returned -19.32%/yr vs 1.49%/yr for FXNAX. Their correlation of 0.93 suggests significant overlap in exposure. SSFEX charges 0.03%/yr vs 0.03%/yr for FXNAX.

Performance

SSFEX vs. FXNAX - Performance Comparison

The chart below illustrates the hypothetical performance of a $10,000 investment in State Street Aggregate Bond Index Fund Class K (SSFEX) and Fidelity U.S. Bond Index Fund (FXNAX). The values are adjusted to include any dividend payments, if applicable.

Returns By Period

As of year-to-date, both investments have demonstrated similar returns, with SSFEX at 0.21% and FXNAX at 0.21%. Over the past 10 years, SSFEX has underperformed FXNAX with an annualized return of -19.32%, while FXNAX has yielded a comparatively higher 1.49% annualized return.

SSFEX

• 1D: -0.21%
• 1M: 0.08%
• YTD: 0.21%
• 6M: 0.32%
• 1Y: 4.54%
• 3Y*: 3.82%
• 5Y*: -0.01%
• 10Y*: -19.32%

FXNAX

• 1D: -0.19%
• 1M: 0.13%
• YTD: 0.21%
• 6M: 0.33%
• 1Y: 4.56%
• 3Y*: 3.95%
• 5Y*: 0.02%
• 10Y*: 1.49%

*Multi-year figures are annualized to reflect compound growth (CAGR)

SSFEX vs. FXNAX - Yearly Performance Comparison

	2026 (YTD)	2025	2024	2023	2022	2021	2020	2019	2018	2017
SSFEX State Street Aggregate Bond Index Fund Class K	0.21%	6.80%	1.35%	5.61%	-13.19%	-1.78%	-89.22%	9.45%	-0.10%	3.30%
FXNAX Fidelity U.S. Bond Index Fund	0.21%	7.14%	1.35%	5.82%	-13.55%	-2.10%	7.63%	8.50%	0.04%	3.50%

Correlation

The correlation between SSFEX and FXNAX 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	0.94
Correlation (5Y) Calculated over the trailing 5-year period	0.96
Correlation (10Y) Calculated over the trailing 10-year period	0.93
Correlation (All Time) Calculated using the full available price history since Sep 23, 2014	0.93

The correlation between SSFEX and FXNAX has been stable across timeframes, ranging from 0.93 to 0.96 - a consistent structural relationship.

Return for Risk

SSFEX vs. FXNAX — Risk / Return Rank

Compare risk-adjusted metric ranks to identify better-performing investments over the past 12 months.

SSFEX

SSFEX Risk / Return Rank: 25
SSFEX Sharpe Ratio Rank: 24
SSFEX Sortino Ratio Rank: 26
SSFEX Omega Ratio Rank: 23
SSFEX Calmar Ratio Rank: 27
SSFEX Martin Ratio Rank: 24

FXNAX

FXNAX Risk / Return Rank: 21
FXNAX Sharpe Ratio Rank: 21
FXNAX Sortino Ratio Rank: 22
FXNAX Omega Ratio Rank: 19
FXNAX Calmar Ratio Rank: 23
FXNAX Martin Ratio Rank: 20

The rank (0–100) shows how this investment's returns compare to the risk taken. Higher = better. Based on the past 12 months of data, combining Sharpe, Sortino, and other metrics used by quantitative funds and institutional investors.

SSFEX vs. FXNAX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for State Street Aggregate Bond Index Fund Class K (SSFEX) 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.

	SSFEX	FXNAX	Difference
Sharpe ratio: Return per unit of total volatility	1.39	1.31	+0.08
Sortino ratio: Return per unit of downside risk	2.08	1.98	+0.11
Omega ratio: Gain probability vs. loss probability	1.25	1.23	+0.01
Calmar ratio: Return relative to maximum drawdown	1.89	1.76	+0.13
Martin ratio: Return relative to average drawdown	5.75	5.37	+0.39
Data is calculated on a 1-year rolling basis and updated daily. The trend shows the change in the indicator over the past month.

SSFEX vs. FXNAX - Sharpe Ratio Comparison

The current SSFEX Sharpe Ratio is 1.39, which is comparable to the FXNAX Sharpe Ratio of 1.31. The chart below compares the historical Sharpe Ratios of SSFEX and FXNAX, calculated using daily returns over the previous 12 months. A higher Sharpe Ratio indicates better risk-adjusted performance relative to the risk-free rate.

Sharpe Ratios by Period

	SSFEX	FXNAX	Difference
Sharpe Ratio (1Y) Calculated over the trailing 1-year period	1.39	1.31	+0.08
Sharpe Ratio (5Y) Calculated over the trailing 5-year period	-0.00	0.00	0.00
Sharpe Ratio (10Y) Calculated over the trailing 10-year period	-0.61	0.30	-0.91
Sharpe Ratio (All Time) Calculated using the full available price history	-0.55	0.45	-1.01

Drawdowns

SSFEX vs. FXNAX - Drawdown Comparison

The maximum SSFEX drawdown since its inception was -92.70%, which is greater than FXNAX's maximum drawdown of -19.51%. Use the drawdown chart below to compare losses from any high point for SSFEX and FXNAX.

Drawdown Indicators

	SSFEX	FXNAX	Difference
Max Drawdown Largest peak-to-trough decline	-92.70%	-19.51%	-73.19%
Max Drawdown (1Y) Largest decline over 1 year	-2.75%	-2.94%	+0.19%
Max Drawdown (3Y) Largest decline over 3 years	-6.09%	-6.16%	+0.07%
Max Drawdown (5Y) Largest decline over 5 years	-17.99%	-18.54%	+0.55%
Max Drawdown (10Y) Largest decline over 10 years	-92.70%	-19.51%	-73.19%
Current Drawdown Current decline from peak	-90.07%	-3.07%	-87.00%
Average Drawdown Average peak-to-trough decline	-48.01%	-3.87%	-44.14%
Ulcer Index Depth and duration of drawdowns from previous peaks	0.90%	0.97%	-0.07%

Volatility

SSFEX vs. FXNAX - Volatility Comparison

The current volatility for State Street Aggregate Bond Index Fund Class K (SSFEX) is 1.27%, while Fidelity U.S. Bond Index Fund (FXNAX) has a volatility of 1.37%. This indicates that SSFEX experiences smaller price fluctuations and is considered to be less risky than FXNAX based on this measure. The chart below showcases a comparison of their rolling one-month volatility.

Volatility by Period

	SSFEX	FXNAX	Difference
Volatility (1M) Calculated over the trailing 1-month period	1.27%	1.37%	-0.10%
Volatility (6M) Calculated over the trailing 6-month period	2.63%	2.80%	-0.17%
Volatility (1Y) Calculated over the trailing 1-year period	3.74%	3.96%	-0.22%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	5.93%	6.07%	-0.14%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	31.83%	5.01%	+26.82%

SSFEX vs. FXNAX - Expense Ratio Comparison

SSFEX has a 0.03% 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

SSFEX vs. FXNAX - Dividend Comparison

SSFEX's dividend yield for the trailing twelve months is around 4.13%, 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%
SSFEX State Street Aggregate Bond Index Fund Class K	4.13%	3.66%	3.76%	3.14%	2.48%	3.32%	9.59%	3.56%	2.79%	2.43%	2.19%	4.67%

Frequently Asked Questions

Can I hold both SSFEX and FXNAX in my portfolio?

With a correlation of 0.93, SSFEX 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.

Which is riskier, SSFEX or FXNAX?

FXNAX has higher volatility (1.37%) compared to SSFEX (1.27%). In terms of maximum drawdown, SSFEX dropped -92.70% vs FXNAX's -19.51%.

Which has better risk-adjusted returns?

SSFEX currently has the higher Sharpe Ratio (1.39 vs 1.31), 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.