SPAXX vs. PMMF

Last updated Apr 2, 2026

Compare and contrast key facts about Fidelity Government Money Market Fund (SPAXX) and iShares Prime Money Market ETF (PMMF).

SPAXX is managed by Fidelity. It was launched on Feb 5, 1990. PMMF is an actively managed fund by BlackRock. It was launched on Feb 4, 2025.

Performance

SPAXX vs. PMMF - Performance Comparison

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

SPAXX vs. PMMF - Yearly Performance Comparison

	2026 (YTD)	2025
SPAXX Fidelity Government Money Market Fund	0.53%	3.61%
PMMF iShares Prime Money Market ETF	0.88%	3.85%

Returns By Period

In the year-to-date period, SPAXX achieves a 0.53% return, which is significantly lower than PMMF's 0.88% return.

SPAXX

• 1D: 0.00%
• 1M: 0.00%
• YTD: 0.53%
• 6M: 1.46%
• 1Y: 3.49%
• 3Y*: 2.14%
• 5Y*: —
• 10Y*: —

PMMF

• 1D: 0.02%
• 1M: 0.27%
• YTD: 0.88%
• 6M: 1.88%
• 1Y: 4.08%
• 3Y*: —
• 5Y*: —
• 10Y*: —

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

SPAXX vs. PMMF - Expense Ratio Comparison

PMMF

iShares Prime Money Market ETF

Return for Risk

SPAXX vs. PMMF — Risk / Return Rank

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

PMMF

PMMF Risk / Return Rank: 100
PMMF Sharpe Ratio Rank: 100
PMMF Sortino Ratio Rank: 100
PMMF Omega Ratio Rank: 100
PMMF Calmar Ratio Rank: 99
PMMF Martin Ratio Rank: 100

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. PMMF - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for Fidelity Government Money Market Fund (SPAXX) and iShares Prime Money Market ETF (PMMF). 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.

	SPAXX	PMMF	Difference
Sharpe ratio Return per unit of total volatility	3.48	13.41	-9.93
Sortino ratio Return per unit of downside risk	—	25.32	—
Omega ratio Gain probability vs. loss probability	—	11.73	—
Calmar ratio Return relative to maximum drawdown	—	31.58	—
Martin ratio Return relative to average drawdown	—	380.28	—
Data is calculated on a 1-year rolling basis and updated daily. The trend shows the change in the indicator over the past month.

SPAXX vs. PMMF - Sharpe Ratio Comparison

The current SPAXX Sharpe Ratio is 3.48, which is lower than the PMMF Sharpe Ratio of 13.41. The chart below compares the historical Sharpe Ratios of SPAXX and PMMF, offering insights into how both investments have performed under varying market conditions. These values are calculated using daily returns over the previous 12 months.

Sharpe Ratios by Period

	SPAXX	PMMF	Difference
Sharpe Ratio (1Y) Calculated over the trailing 1-year period	3.48	13.41	-9.93
Sharpe Ratio (All Time) Calculated using the full available price history	2.01	11.54	-9.53

Correlation

The correlation between SPAXX and PMMF is -0.01. This indicates that the assets' prices tend to move in opposite directions. Negative correlation can be particularly beneficial for diversification and risk management, as one asset may offset the losses of the other during market fluctuations.

Dividends

SPAXX vs. PMMF - Dividend Comparison

SPAXX's dividend yield for the trailing twelve months is around 3.42%, less than PMMF's 3.88% yield.

	TTM	2025	2024	2023
SPAXX Fidelity Government Money Market Fund	3.42%	3.88%	1.53%	0.41%
PMMF iShares Prime Money Market ETF	3.88%	3.59%	0.00%	0.00%

Drawdowns

SPAXX vs. PMMF - Drawdown Comparison

The maximum SPAXX drawdown since its inception was 0.00%, smaller than the maximum PMMF drawdown of -0.13%. Use the drawdown chart below to compare losses from any high point for SPAXX and PMMF.

Drawdown Indicators

	SPAXX	PMMF	Difference
Max Drawdown Largest peak-to-trough decline	0.00%	-0.13%	+0.13%
Max Drawdown (1Y) Largest decline over 1 year	0.00%	-0.13%	+0.13%
Current Drawdown Current decline from peak	0.00%	0.00%	0.00%
Average Drawdown Average peak-to-trough decline	0.00%	0.00%	0.00%
Ulcer Index Depth and duration of drawdowns from previous peaks	0.00%	0.01%	-0.01%

Volatility

SPAXX vs. PMMF - Volatility Comparison

The current volatility for Fidelity Government Money Market Fund (SPAXX) is 0.00%, while iShares Prime Money Market ETF (PMMF) has a volatility of 0.05%. This indicates that SPAXX experiences smaller price fluctuations and is considered to be less risky than PMMF based on this measure. The chart below showcases a comparison of their rolling one-month volatility.

Volatility by Period

	SPAXX	PMMF	Difference
Volatility (1M) Calculated over the trailing 1-month period	0.00%	0.05%	-0.05%
Volatility (6M) Calculated over the trailing 6-month period	0.71%	0.13%	+0.58%
Volatility (1Y) Calculated over the trailing 1-year period	1.08%	0.31%	+0.77%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	0.67%	0.36%	+0.31%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	0.67%	0.36%	+0.31%