MIAIX vs. FSPWX

Last updated Jun 4, 2026

MIAIX (MFS Inflation-Adjusted Bond Fund) and FSPWX (Fidelity SAI Inflation-Protected Bond Index Fund) are both Inflation-Protected Bonds funds. Over the past year, MIAIX returned 4.58% vs 5.38% for FSPWX. Their correlation of 0.93 suggests significant overlap in exposure. MIAIX charges 0.49%/yr vs 0.05%/yr for FSPWX.

Performance

MIAIX vs. FSPWX - Performance Comparison

The chart below illustrates the hypothetical performance of a $10,000 investment in MFS Inflation-Adjusted Bond Fund (MIAIX) and Fidelity SAI Inflation-Protected Bond Index Fund (FSPWX). The values are adjusted to include any dividend payments, if applicable.

Returns By Period

In the year-to-date period, MIAIX achieves a 1.33% return, which is significantly lower than FSPWX's 1.83% return.

MIAIX

• 1D: 0.00%
• 1M: 0.00%
• YTD: 1.33%
• 6M: 0.78%
• 1Y: 4.58%
• 3Y*: 3.21%
• 5Y*: 0.45%
• 10Y*: 2.07%

FSPWX

• 1D: 0.00%
• 1M: 0.20%
• YTD: 1.83%
• 6M: 1.35%
• 1Y: 5.38%
• 3Y*: —
• 5Y*: —
• 10Y*: —

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

MIAIX vs. FSPWX - Yearly Performance Comparison

	2026 (YTD)	2025	2024
MIAIX MFS Inflation-Adjusted Bond Fund	1.33%	5.89%	-1.62%
FSPWX Fidelity SAI Inflation-Protected Bond Index Fund	1.83%	6.76%	-1.32%

Correlation

The correlation between MIAIX and FSPWX is 0.93, indicating a strong positive relationship between their price movements. Combining them offers limited diversification - they tend to fall together during downturns.

	Correlation
Correlation (1Y) Calculated over the trailing 1-year period	0.93
Correlation (All Time) Calculated using the full available price history since Aug 23, 2024	0.93

The correlation between MIAIX and FSPWX has been stable across timeframes, ranging from 0.93 to 0.93 - a consistent structural relationship.

Return for Risk

MIAIX vs. FSPWX — Risk / Return Rank

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

MIAIX

MIAIX Risk / Return Rank: 23
MIAIX Sharpe Ratio Rank: 20
MIAIX Sortino Ratio Rank: 22
MIAIX Omega Ratio Rank: 19
MIAIX Calmar Ratio Rank: 30
MIAIX Martin Ratio Rank: 25

FSPWX

FSPWX Risk / Return Rank: 36
FSPWX Sharpe Ratio Rank: 30
FSPWX Sortino Ratio Rank: 33
FSPWX Omega Ratio Rank: 30
FSPWX Calmar Ratio Rank: 49
FSPWX Martin Ratio Rank: 37

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.

MIAIX vs. FSPWX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for MFS Inflation-Adjusted Bond Fund (MIAIX) and Fidelity SAI Inflation-Protected Bond Index Fund (FSPWX). 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.

	MIAIX	FSPWX	Difference
Sharpe ratio Return per unit of total volatility	1.28	1.56	-0.28
Sortino ratio Return per unit of downside risk	1.97	2.39	-0.42
Omega ratio Gain probability vs. loss probability	1.23	1.29	-0.06
Calmar ratio Return relative to maximum drawdown	2.06	2.67	-0.62
Martin ratio Return relative to average drawdown	6.15	8.19	-2.04
Data is calculated on a 1-year rolling basis and updated daily. The trend shows the change in the indicator over the past month.

MIAIX vs. FSPWX - Sharpe Ratio Comparison

The current MIAIX Sharpe Ratio is 1.28, which is comparable to the FSPWX Sharpe Ratio of 1.56. The chart below compares the historical Sharpe Ratios of MIAIX and FSPWX, calculated using daily returns over the previous 12 months. A higher Sharpe Ratio indicates better risk-adjusted performance relative to the risk-free rate.

Sharpe Ratios by Period

	MIAIX	FSPWX	Difference
Sharpe Ratio (1Y) Calculated over the trailing 1-year period	1.28	1.56	-0.28
Sharpe Ratio (5Y) Calculated over the trailing 5-year period	0.07	—	—
Sharpe Ratio (10Y) Calculated over the trailing 10-year period	0.38	—	—
Sharpe Ratio (All Time) Calculated using the full available price history	0.49	1.00	-0.52

Drawdowns

MIAIX vs. FSPWX - Drawdown Comparison

The maximum MIAIX drawdown since its inception was -15.99%, which is greater than FSPWX's maximum drawdown of -3.84%. Use the drawdown chart below to compare losses from any high point for MIAIX and FSPWX.

Drawdown Indicators

	MIAIX	FSPWX	Difference
Max Drawdown Largest peak-to-trough decline	-15.99%	-3.84%	-12.15%
Max Drawdown (1Y) Largest decline over 1 year	-2.18%	-1.95%	-0.23%
Max Drawdown (3Y) Largest decline over 3 years	-5.64%	—	—
Max Drawdown (5Y) Largest decline over 5 years	-15.99%	—	—
Max Drawdown (10Y) Largest decline over 10 years	-15.99%	—	—
Current Drawdown Current decline from peak	-2.32%	0.00%	-2.32%
Average Drawdown Average peak-to-trough decline	-4.25%	-0.98%	-3.27%
Ulcer Index Depth and duration of drawdowns from previous peaks	0.73%	0.64%	+0.09%

Volatility

MIAIX vs. FSPWX - Volatility Comparison

MFS Inflation-Adjusted Bond Fund (MIAIX) and Fidelity SAI Inflation-Protected Bond Index Fund (FSPWX) have volatilities of 0.94% and 0.92%, respectively, indicating that both stocks experience similar levels of price fluctuations. This suggests that the risk associated with both stocks, as measured by volatility, is nearly the same. The chart below showcases a comparison of their rolling one-month volatility.

Volatility by Period

	MIAIX	FSPWX	Difference
Volatility (1M) Calculated over the trailing 1-month period	0.94%	0.92%	+0.02%
Volatility (6M) Calculated over the trailing 6-month period	2.41%	2.28%	+0.13%
Volatility (1Y) Calculated over the trailing 1-year period	3.52%	3.35%	+0.17%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	6.18%	4.06%	+2.12%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	5.48%	4.06%	+1.42%

MIAIX vs. FSPWX - Expense Ratio Comparison

MIAIX has a 0.49% expense ratio, which is higher than FSPWX's 0.05% expense ratio.

Dividends

MIAIX vs. FSPWX - Dividend Comparison

MIAIX's dividend yield for the trailing twelve months is around 4.05%, more than FSPWX's 3.76% yield.

Position	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017	2016	2015
FSPWX Fidelity SAI Inflation-Protected Bond Index Fund	3.76%	4.19%	0.69%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%	0.00%
MIAIX MFS Inflation-Adjusted Bond Fund	4.05%	4.10%	4.10%	4.00%	7.96%	5.10%	1.45%	2.18%	2.85%	2.14%	1.82%	0.67%

Frequently Asked Questions

Can I hold both MIAIX and FSPWX in my portfolio?

With a correlation of 0.93, MIAIX and FSPWX move almost identically. Holding both adds very little diversification - you're essentially doubling your position in the same market segment. Choosing one is usually more capital-efficient.

Which is riskier, MIAIX or FSPWX?

MIAIX has higher volatility (0.94%) compared to FSPWX (0.92%). In terms of maximum drawdown, MIAIX dropped -15.99% vs FSPWX's -3.84%.

Which has better risk-adjusted returns?

FSPWX currently has the higher Sharpe Ratio (1.56 vs 1.28), 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.