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SPAXX vs. IUSB
Performance
Return for Risk
Drawdowns
Volatility
Dividends

SPAXX vs. IUSB

Last updated Jun 13, 2026

SPAXX (Fidelity Government Money Market Fund) and IUSB (iShares Core Universal USD Bond ETF) are both funds - SPAXX is a Money Market fund actively managed by Fidelity, while IUSB is a Intermediate Core-Plus Bond fund tracking the Bloomberg U.S. Universal Index. SPAXX is actively managed, while IUSB is passively managed. Over the past 5 years, SPAXX returned 1.45%/yr vs 0.39%/yr for IUSB. At a 0.02 correlation, their price movements are largely independent. SPAXX charges 0.42%/yr vs 0.06%/yr for IUSB.

Performance

SPAXX vs. IUSB - Performance Comparison

The chart below illustrates the hypothetical performance of a $10,000 investment in Fidelity Government Money Market Fund (SPAXX) and iShares Core Universal USD Bond ETF (IUSB). The values are adjusted to include any dividend payments, if applicable.

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Returns By Period

In the year-to-date period, SPAXX achieves a 1.37% return, which is significantly higher than IUSB's 0.67% return.

SPAXX

1D
0.00%
1M
0.28%
YTD
1.37%
6M
1.67%
1Y
3.66%
3Y*
2.42%
5Y*
1.45%
10Y*
—

IUSB

1D
-0.07%
1M
0.46%
YTD
0.67%
6M
1.05%
1Y
4.82%
3Y*
4.70%
5Y*
0.39%
10Y*
1.97%
*Multi-year figures are annualized to reflect compound growth (CAGR)

SPAXX vs. IUSB - Yearly Performance Comparison

2026 (YTD)20252024202320222021
SPAXX
Fidelity Government Money Market Fund		1.37%3.96%1.54%0.41%0.00%0.00%
IUSB
iShares Core Universal USD Bond ETF		0.67%7.38%2.11%6.23%-13.04%0.85%

Correlation

The correlation between SPAXX and IUSB is 0.00, meaning there is essentially no relationship between their price movements. Each responds to its own set of market drivers, making them strong candidates for combining in a diversified portfolio.

Correlation
Correlation (1Y)
Calculated over the trailing 1-year period

0.00

Correlation (3Y)
Calculated over the trailing 3-year period

0.02

Correlation (5Y)
Calculated over the trailing 5-year period

0.02

Correlation (All Time)
Calculated using the full available price history since May 25, 2021

0.02

Compare stocks, funds, or ETFs

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Fidelity Government Money Market Fund

iShares Core Universal USD Bond ETF

Often compared with SPAXX:
SPAXX vs. SGOVSPAXX vs. VMFXXSPAXX vs. SNSXXSPAXX vs. SWVXXSPAXX vs. BILSPAXX vs. BNDSPAXX vs. TFLO
Often compared with IUSB:
IUSB vs. BNDIUSB vs. AGGIUSB vs. FBNDIUSB vs. IAGGIUSB vs. ICSHIUSB vs. IXUSIUSB vs. FLOT

Return for Risk

SPAXX vs. IUSB — Risk / Return Rank

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

Risk / return metrics aren't available yet — we need at least 12 months of trading data to calculate them.

IUSB
IUSB Risk / Return Rank: 4343
Overall Rank
IUSB Sharpe Ratio Rank: 4444
Sharpe Ratio Rank
IUSB Sortino Ratio Rank: 4545
Sortino Ratio Rank
IUSB Omega Ratio Rank: 4242
Omega Ratio Rank
IUSB Calmar Ratio Rank: 4444
Calmar Ratio Rank
IUSB Martin Ratio Rank: 4040
Martin Ratio Rank
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.

SPAXX vs. IUSB - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for Fidelity Government Money Market Fund (SPAXX) and iShares Core Universal USD Bond ETF (IUSB). 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.

SPAXXIUSBDifference
Sharpe ratioReturn per unit of total volatility
3.65
1.35

+2.29

Sortino ratioReturn per unit of downside risk

—

2.02

—

Omega ratioGain probability vs. loss probability

—

1.24

—

Calmar ratioReturn relative to maximum drawdown

—

1.92

—

Martin ratioReturn relative to average drawdown

—

5.62

—

SPAXX vs. IUSB - Sharpe Ratio Comparison

The current SPAXX Sharpe Ratio is 3.65, which is higher than the IUSB Sharpe Ratio of 1.35. The chart below compares the historical Sharpe Ratios of SPAXX and IUSB, calculated using daily returns over the previous 12 months. A higher Sharpe Ratio indicates better risk-adjusted performance relative to the risk-free rate.

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Drawdowns

SPAXX vs. IUSB - Drawdown Comparison

The maximum SPAXX drawdown since its inception was 0.00%, smaller than the maximum IUSB drawdown of -17.90%. Use the drawdown chart below to compare losses from any high point for SPAXX and IUSB.

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Drawdown Indicators

SPAXXIUSBDifference

Max Drawdown

Largest peak-to-trough decline

0.00%

-17.90%

+17.90%

Max Drawdown (1Y)

Largest decline over 1 year

0.00%

-2.53%

+2.53%

Max Drawdown (3Y)

Largest decline over 3 years

0.00%

-5.82%

+5.82%

Max Drawdown (5Y)

Largest decline over 5 years

0.00%

-17.87%

+17.87%

Max Drawdown (10Y)

Largest decline over 10 years

—

-17.90%

—

Current Drawdown

Current decline from peak

0.00%

-1.09%

+1.09%

Average Drawdown

Average peak-to-trough decline

0.00%

-3.58%

+3.58%

Ulcer Index

Depth and duration of drawdowns from previous peaks

0.00%

0.86%

-0.86%

Volatility

SPAXX vs. IUSB - Volatility Comparison

The current volatility for Fidelity Government Money Market Fund (SPAXX) is 0.28%, while iShares Core Universal USD Bond ETF (IUSB) has a volatility of 1.30%. This indicates that SPAXX experiences smaller price fluctuations and is considered to be less risky than IUSB based on this measure. The chart below showcases a comparison of their rolling one-month volatility.

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Volatility by Period

SPAXXIUSBDifference

Volatility (1M)

Calculated over the trailing 1-month period

0.28%

1.30%

-1.02%

Volatility (6M)

Calculated over the trailing 6-month period

0.66%

2.69%

-2.03%

Volatility (1Y)

Calculated over the trailing 1-year period

1.03%

3.59%

-2.56%

Volatility (5Y)

Calculated over the trailing 5-year period, annualized

0.69%

5.80%

-5.11%

Volatility (10Y)

Calculated over the trailing 10-year period, annualized

0.69%

5.04%

-4.35%

SPAXX vs. IUSB - Expense Ratio Comparison

SPAXX has a 0.42% expense ratio, which is higher than IUSB's 0.06% expense ratio.

Dividends

SPAXX vs. IUSB - Dividend Comparison

SPAXX's dividend yield for the trailing twelve months is around 3.59%, less than IUSB's 4.22% yield.

PositionTTM20252024202320222021202020192018201720162015
IUSB
iShares Core Universal USD Bond ETF		4.22%4.17%4.04%3.46%2.53%1.74%2.68%3.04%2.98%2.56%2.60%1.95%
SPAXX
Fidelity Government Money Market Fund		3.59%3.88%1.53%0.41%0.00%0.00%0.00%0.00%0.00%0.00%0.00%0.00%

Frequently Asked Questions

SPAXX and IUSB have a correlation of 0.00, meaning they provide meaningful diversification benefit when combined. Depending on your allocation goals, holding both could reduce overall portfolio risk.

IUSB has higher volatility (1.30%) compared to SPAXX (0.28%). In terms of maximum drawdown, SPAXX dropped 0.00% vs IUSB's -17.90%.

SPAXX currently has the higher Sharpe Ratio (3.65 vs 1.35), 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.

Portfolio Optimizer

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