SPAXX vs. PMMF
SPAXX (Fidelity Government Money Market Fund) and PMMF (iShares Prime Money Market ETF) are both Money Market funds. Both are actively managed. Over the past year, SPAXX returned 3.66% vs 4.00% for PMMF. At a 0.01 correlation, their price movements are largely independent. SPAXX charges 0.42%/yr vs 0.20%/yr for PMMF.
Performance
SPAXX vs. PMMF - Performance Comparison
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Returns By Period
In the year-to-date period, SPAXX achieves a 1.37% return, which is significantly lower than PMMF's 1.52% return.
SPAXX
- 1D
- 0.00%
- 1M
- 0.28%
- YTD
- 1.37%
- 6M
- 1.67%
- 1Y
- 3.66%
- 3Y*
- 2.42%
- 5Y*
- 1.45%
- 10Y*
- —
PMMF
- 1D
- 0.01%
- 1M
- 0.30%
- YTD
- 1.52%
- 6M
- 1.82%
- 1Y
- 4.00%
- 3Y*
- —
- 5Y*
- —
- 10Y*
- —
SPAXX vs. PMMF - Yearly Performance Comparison
| 2026 (YTD) | 2025 | |
|---|---|---|
SPAXX Fidelity Government Money Market Fund | 1.37% | 3.61% |
PMMF iShares Prime Money Market ETF | 1.52% | 3.85% |
Correlation
The correlation between SPAXX and PMMF is -0.01, 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 | -0.01 |
Correlation (All Time) Calculated using the full available price history since Feb 7, 2025 | 0.01 |
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Return for Risk
SPAXX vs. PMMF — Risk / Return Rank
SPAXX
PMMF
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 ratioReturn per unit of total volatility | -16.07 | ||
| Sortino ratioReturn per unit of downside risk | — | — | |
| Omega ratioGain probability vs. loss probability | — | 38.37 | — |
| Calmar ratioReturn relative to maximum drawdown | — | 161.17 | — |
| Martin ratioReturn relative to average drawdown | — | 1,488.23 | — |
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
| SPAXX | PMMF | Difference | |
|---|---|---|---|
Sharpe Ratio (1Y)Calculated over the trailing 1-year period | 3.65 | 19.72 | -16.07 |
Sharpe Ratio (5Y)Calculated over the trailing 5-year period | 2.13 | — | — |
Sharpe Ratio (All Time)Calculated using the full available price history | 2.13 | 11.97 | -9.85 |
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.
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Drawdown Indicators
| SPAXX | PMMF | Difference | |
|---|---|---|---|
Max DrawdownLargest peak-to-trough decline | 0.00% | -0.13% | +0.13% |
Max Drawdown (1Y)Largest decline over 1 year | 0.00% | -0.02% | +0.02% |
Max Drawdown (3Y)Largest decline over 3 years | 0.00% | — | — |
Max Drawdown (5Y)Largest decline over 5 years | 0.00% | — | — |
Current DrawdownCurrent decline from peak | 0.00% | 0.00% | 0.00% |
Average DrawdownAverage peak-to-trough decline | 0.00% | -0.00% | 0.00% |
Ulcer IndexDepth and duration of drawdowns from previous peaks | 0.00% | 0.00% | 0.00% |
Volatility
SPAXX vs. PMMF - Volatility Comparison
Fidelity Government Money Market Fund (SPAXX) has a higher volatility of 0.28% compared to iShares Prime Money Market ETF (PMMF) at 0.05%. This indicates that SPAXX's price experiences larger fluctuations and is considered to be riskier than PMMF based on this measure. The chart below showcases a comparison of their rolling one-month volatility.
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Volatility by Period
| SPAXX | PMMF | Difference | |
|---|---|---|---|
Volatility (1M)Calculated over the trailing 1-month period | 0.28% | 0.05% | +0.23% |
Volatility (6M)Calculated over the trailing 6-month period | 0.72% | 0.12% | +0.60% |
Volatility (1Y)Calculated over the trailing 1-year period | 1.03% | 0.20% | +0.83% |
Volatility (5Y)Calculated over the trailing 5-year period, annualized | 0.69% | 0.34% | +0.35% |
Volatility (10Y)Calculated over the trailing 10-year period, annualized | 0.69% | 0.34% | +0.35% |
SPAXX vs. PMMF - Expense Ratio Comparison
SPAXX has a 0.42% expense ratio, which is higher than PMMF's 0.20% expense ratio.
Dividends
SPAXX vs. PMMF - Dividend Comparison
SPAXX's dividend yield for the trailing twelve months is around 3.59%, less than PMMF's 3.83% yield.
| Position | TTM | 2025 | 2024 | 2023 |
|---|---|---|---|---|
PMMF iShares Prime Money Market ETF | 3.83% | 3.59% | 0.00% | 0.00% |
SPAXX Fidelity Government Money Market Fund | 3.59% | 3.88% | 1.53% | 0.41% |
Frequently Asked Questions
SPAXX and PMMF have a correlation of -0.01, meaning they provide meaningful diversification benefit when combined. Depending on your allocation goals, holding both could reduce overall portfolio risk.
SPAXX has higher volatility (0.28%) compared to PMMF (0.05%). In terms of maximum drawdown, SPAXX dropped 0.00% vs PMMF's -0.13%.
PMMF currently has the higher Sharpe Ratio (19.72 vs 3.65), 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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