PMMF vs. SPAXX
PMMF (iShares Prime Money Market ETF) and SPAXX (Fidelity Government Money Market Fund) are both Money Market funds. Both are actively managed. Over the past year, PMMF returned 3.89% vs 3.25% for SPAXX. Their -0.01 correlation means they have often moved in opposite directions in the past. PMMF charges 0.20%/yr vs 0.42%/yr for SPAXX.
Performance
PMMF vs. SPAXX - Performance Comparison
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Returns By Period
In the year-to-date period, PMMF achieves a 2.14% return, which is significantly higher than SPAXX's 1.64% return.
PMMF
- 1D
- 0.02%
- 1M
- 0.31%
- 6M
- 1.81%
- YTD
- 2.14%
- 1Y
- 3.89%
- 3Y*
- —
- 5Y*
- —
- 10Y*
- —
- ALL TIME*
- 3.98%
SPAXX
- 1D
- 0.00%
- 1M
- 0.00%
- 6M
- 1.35%
- YTD
- 1.64%
- 1Y
- 3.25%
- 3Y*
- 2.52%
- 5Y*
- 1.50%
- 10Y*
- —
- ALL TIME*
- 1.45%
Liquidity Comparison
| Position | Avg. Volume Value (2W) | Avg. Volume Value (1M) | Avg. Volume Value (3M) |
|---|---|---|---|
| $11.61M | $12.34M | $15.91M | |
| $0.00 | $0.00 | $0.00 |
PMMF vs. SPAXX - Yearly Performance Comparison
| 2026 (YTD) | 2025 | |
|---|---|---|
PMMF iShares Prime Money Market ETF | 2.14% | 3.75% |
SPAXX Fidelity Government Money Market Fund | 1.64% | 3.61% |
Correlation
The correlation between PMMF and SPAXX is 0.00, meaning there was essentially no consistent relationship between their historical price movements. Each responded to its own set of market drivers.
| Correlation | |
|---|---|
Correlation (1Y) Focuses on recent behavior, but can change the most. | 0.00 |
Correlation (All Time) Calculated using the full available price history since Feb 6, 2025 | -0.01 |
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Return for Risk
PMMF vs. SPAXX — Risk / Return Rank
PMMF
SPAXX
Risk / return metrics aren't available yet — we need at least 12 months of trading data to calculate them.
PMMF vs. SPAXX - Risk-Adjusted Trends Comparison
This table presents a comparison of risk-adjusted performance metrics for iShares Prime Money Market ETF (PMMF) 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.
| PMMF | SPAXX | Difference | |
|---|---|---|---|
| Sharpe ratioReturn per unit of total volatility | +17.53 | ||
| Sortino ratioReturn per unit of downside risk | — | — | |
| Omega ratioGain probability vs. loss probability | 50.57 | — | — |
| Calmar ratioReturn relative to maximum drawdown | 156.87 | — | — |
| Martin ratioReturn relative to average drawdown | 1,677.66 | — | — |
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Drawdowns
PMMF vs. SPAXX - Drawdown Comparison
The maximum PMMF drawdown since its inception was -0.13%, which is greater than SPAXX's maximum drawdown of 0.00%. Use the drawdown chart below to compare losses from any high point for PMMF and SPAXX.
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Drawdown Indicators
| PMMF | SPAXX | Difference | |
|---|---|---|---|
Max DrawdownLargest peak-to-trough decline | -0.13% | 0.00% | -0.13% |
Max Drawdown (1Y)Largest decline over 1 year | -0.02% | 0.00% | -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
PMMF vs. SPAXX - Volatility Comparison
iShares Prime Money Market ETF (PMMF) has a higher volatility of 0.05% compared to Fidelity Government Money Market Fund (SPAXX) at 0.00%. This indicates that PMMF'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
| PMMF | SPAXX | Difference | |
|---|---|---|---|
Volatility (1M)Calculated over the trailing 1-month period | 0.05% | 0.00% | +0.05% |
Volatility (6M)Calculated over the trailing 6-month period | 0.13% | 0.65% | -0.52% |
Volatility (1Y)Calculated over the trailing 1-year period | 0.19% | 1.02% | -0.83% |
Volatility (5Y)Calculated over the trailing 5-year period, annualized | 0.34% | 0.70% | -0.36% |
Volatility (10Y)Calculated over the trailing 10-year period, annualized | 0.34% | 0.69% | -0.35% |
PMMF vs. SPAXX - Expense Ratio Comparison
PMMF has a 0.20% expense ratio, which is lower than SPAXX's 0.42% expense ratio.
Dividends
PMMF vs. SPAXX - Dividend Comparison
PMMF's dividend yield for the trailing twelve months is around 3.69%, more than SPAXX's 3.20% yield.
| Position | TTM | 2025 | 2024 | 2023 |
|---|---|---|---|---|
PMMF iShares Prime Money Market ETF | 3.69% | 3.59% | 0.00% | 0.00% |
SPAXX Fidelity Government Money Market Fund | 3.20% | 3.88% | 1.53% | 0.41% |
Frequently Asked Questions
PMMF 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.
PMMF has higher volatility (0.05%) compared to SPAXX (0.00%). In terms of maximum drawdown, PMMF dropped -0.13% vs SPAXX's 0.00%.
PMMF currently has the higher Sharpe Ratio (21.01 vs 3.48), 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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