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IUSB vs. SPAXX
Performance
Return for Risk
Drawdowns
Volatility
Dividends

IUSB vs. SPAXX

Last updated Jun 13, 2026

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

Performance

IUSB vs. SPAXX - Performance Comparison

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

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Returns By Period

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

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%

SPAXX

1D
0.00%
1M
0.28%
YTD
1.37%
6M
1.67%
1Y
3.66%
3Y*
2.42%
5Y*
1.45%
10Y*
—
*Multi-year figures are annualized to reflect compound growth (CAGR)

IUSB vs. SPAXX - Yearly Performance Comparison

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

Correlation

The correlation between IUSB and SPAXX 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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iShares Core Universal USD Bond ETF

Fidelity Government Money Market Fund

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

Return for Risk

IUSB vs. SPAXX — Risk / Return Rank

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

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

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.

IUSB vs. SPAXX - Risk-Adjusted Trends Comparison

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

IUSBSPAXXDifference
Sharpe ratioReturn per unit of total volatility
1.35
3.65

-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

—

—

IUSB vs. SPAXX - Sharpe Ratio Comparison

The current IUSB Sharpe Ratio is 1.35, which is lower than the SPAXX Sharpe Ratio of 3.65. The chart below compares the historical Sharpe Ratios of IUSB and SPAXX, 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

IUSB vs. SPAXX - Drawdown Comparison

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

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Drawdown Indicators

IUSBSPAXXDifference

Max Drawdown

Largest peak-to-trough decline

-17.90%

0.00%

-17.90%

Max Drawdown (1Y)

Largest decline over 1 year

-2.53%

0.00%

-2.53%

Max Drawdown (3Y)

Largest decline over 3 years

-5.82%

0.00%

-5.82%

Max Drawdown (5Y)

Largest decline over 5 years

-17.87%

0.00%

-17.87%

Max Drawdown (10Y)

Largest decline over 10 years

-17.90%

—

—

Current Drawdown

Current decline from peak

-1.09%

0.00%

-1.09%

Average Drawdown

Average peak-to-trough decline

-3.58%

0.00%

-3.58%

Ulcer Index

Depth and duration of drawdowns from previous peaks

0.86%

0.00%

+0.86%

Volatility

IUSB vs. SPAXX - Volatility Comparison

iShares Core Universal USD Bond ETF (IUSB) has a higher volatility of 1.30% compared to Fidelity Government Money Market Fund (SPAXX) at 0.28%. This indicates that IUSB's price experiences larger fluctuations and is considered to be riskier than SPAXX based on this measure. The chart below showcases a comparison of their rolling one-month volatility.

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Volatility by Period

IUSBSPAXXDifference

Volatility (1M)

Calculated over the trailing 1-month period

1.30%

0.28%

+1.02%

Volatility (6M)

Calculated over the trailing 6-month period

2.69%

0.66%

+2.03%

Volatility (1Y)

Calculated over the trailing 1-year period

3.59%

1.03%

+2.56%

Volatility (5Y)

Calculated over the trailing 5-year period, annualized

5.80%

0.69%

+5.11%

Volatility (10Y)

Calculated over the trailing 10-year period, annualized

5.04%

0.69%

+4.35%

IUSB vs. SPAXX - Expense Ratio Comparison

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

Dividends

IUSB vs. SPAXX - Dividend Comparison

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

IUSB and SPAXX 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, IUSB dropped -17.90% vs SPAXX's 0.00%.

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.

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