FSPWX vs. APOIX

Last updated Jun 4, 2026

FSPWX (Fidelity SAI Inflation-Protected Bond Index Fund) and APOIX (American Century Short Duration Inflation Protection Bond Fund Investor Class) are both Inflation-Protected Bonds funds. Over the past year, FSPWX returned 5.38% vs 4.51% for APOIX. A 0.74 correlation means they provide meaningful diversification when combined. FSPWX charges 0.05%/yr vs 0.57%/yr for APOIX.

Performance

FSPWX vs. APOIX - Performance Comparison

The chart below illustrates the hypothetical performance of a $10,000 investment in Fidelity SAI Inflation-Protected Bond Index Fund (FSPWX) and American Century Short Duration Inflation Protection Bond Fund Investor Class (APOIX). The values are adjusted to include any dividend payments, if applicable.

Returns By Period

In the year-to-date period, FSPWX achieves a 1.83% return, which is significantly lower than APOIX's 2.02% return.

FSPWX

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

APOIX

• 1D: 0.00%
• 1M: -0.00%
• YTD: 2.02%
• 6M: 1.90%
• 1Y: 4.51%
• 3Y*: 4.85%
• 5Y*: 2.96%
• 10Y*: 3.13%

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

FSPWX vs. APOIX - Yearly Performance Comparison

	2026 (YTD)	2025	2024
FSPWX Fidelity SAI Inflation-Protected Bond Index Fund	1.83%	6.76%	-1.32%
APOIX American Century Short Duration Inflation Protection Bond Fund Investor Class	2.02%	5.95%	0.88%

Correlation

The correlation between FSPWX and APOIX is 0.72, which is moderate. They share some common price drivers but move independently often enough to provide real diversification benefit when combined.

	Correlation
Correlation (1Y) Calculated over the trailing 1-year period	0.72
Correlation (All Time) Calculated using the full available price history since Aug 23, 2024	0.74

The correlation between FSPWX and APOIX has been stable across timeframes, ranging from 0.72 to 0.74 - a consistent structural relationship.

Return for Risk

FSPWX vs. APOIX — Risk / Return Rank

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

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

APOIX

APOIX Risk / Return Rank: 84
APOIX Sharpe Ratio Rank: 71
APOIX Sortino Ratio Rank: 84
APOIX Omega Ratio Rank: 78
APOIX Calmar Ratio Rank: 95
APOIX Martin Ratio Rank: 91

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.

FSPWX vs. APOIX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for Fidelity SAI Inflation-Protected Bond Index Fund (FSPWX) and American Century Short Duration Inflation Protection Bond Fund Investor Class (APOIX). 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.

	FSPWX	APOIX	Difference
Sharpe ratio: Return per unit of total volatility	1.56	2.45	-0.89
Sortino ratio: Return per unit of downside risk	2.39	4.00	-1.61
Omega ratio: Gain probability vs. loss probability	1.29	1.51	-0.22
Calmar ratio: Return relative to maximum drawdown	2.67	5.81	-3.14
Martin ratio: Return relative to average drawdown	8.19	19.09	-10.90
Data is calculated on a 1-year rolling basis and updated daily. The trend shows the change in the indicator over the past month.

FSPWX vs. APOIX - Sharpe Ratio Comparison

The current FSPWX Sharpe Ratio is 1.56, which is lower than the APOIX Sharpe Ratio of 2.45. The chart below compares the historical Sharpe Ratios of FSPWX and APOIX, 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

	FSPWX	APOIX	Difference
Sharpe Ratio (1Y) Calculated over the trailing 1-year period	1.56	2.45	-0.89
Sharpe Ratio (5Y) Calculated over the trailing 5-year period	—	0.90	—
Sharpe Ratio (10Y) Calculated over the trailing 10-year period	—	1.10	—
Sharpe Ratio (All Time) Calculated using the full available price history	1.00	0.72	+0.29

Drawdowns

FSPWX vs. APOIX - Drawdown Comparison

The maximum FSPWX drawdown since its inception was -3.84%, smaller than the maximum APOIX drawdown of -14.54%. Use the drawdown chart below to compare losses from any high point for FSPWX and APOIX.

Drawdown Indicators

	FSPWX	APOIX	Difference
Max Drawdown Largest peak-to-trough decline	-3.84%	-14.54%	+10.70%
Max Drawdown (1Y) Largest decline over 1 year	-1.95%	-0.76%	-1.19%
Max Drawdown (3Y) Largest decline over 3 years	—	-1.42%	—
Max Drawdown (5Y) Largest decline over 5 years	—	-6.58%	—
Max Drawdown (10Y) Largest decline over 10 years	—	-6.58%	—
Current Drawdown Current decline from peak	0.00%	-0.00%	0.00%
Average Drawdown Average peak-to-trough decline	-0.98%	-1.99%	+1.01%
Ulcer Index Depth and duration of drawdowns from previous peaks	0.64%	0.23%	+0.41%

Volatility

FSPWX vs. APOIX - Volatility Comparison

Fidelity SAI Inflation-Protected Bond Index Fund (FSPWX) has a higher volatility of 0.92% compared to American Century Short Duration Inflation Protection Bond Fund Investor Class (APOIX) at 0.51%. This indicates that FSPWX's price experiences larger fluctuations and is considered to be riskier than APOIX based on this measure. The chart below showcases a comparison of their rolling one-month volatility.

Volatility by Period

	FSPWX	APOIX	Difference
Volatility (1M) Calculated over the trailing 1-month period	0.92%	0.51%	+0.41%
Volatility (6M) Calculated over the trailing 6-month period	2.28%	1.25%	+1.03%
Volatility (1Y) Calculated over the trailing 1-year period	3.35%	1.81%	+1.54%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	4.06%	3.31%	+0.75%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	4.06%	2.85%	+1.21%

FSPWX vs. APOIX - Expense Ratio Comparison

FSPWX has a 0.05% expense ratio, which is lower than APOIX's 0.57% expense ratio.

Dividends

FSPWX vs. APOIX - Dividend Comparison

FSPWX's dividend yield for the trailing twelve months is around 3.76%, less than APOIX's 3.91% yield.

Position	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017	2016
APOIX American Century Short Duration Inflation Protection Bond Fund Investor Class	3.91%	3.99%	2.31%	2.78%	5.63%	3.92%	0.81%	1.69%	3.99%	1.52%	0.42%
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%

Frequently Asked Questions

Can I hold both FSPWX and APOIX in my portfolio?

FSPWX and APOIX have a correlation of 0.72, meaning they provide meaningful diversification benefit when combined. Depending on your allocation goals, holding both could reduce overall portfolio risk.

Which is riskier, FSPWX or APOIX?

FSPWX has higher volatility (0.92%) compared to APOIX (0.51%). In terms of maximum drawdown, FSPWX dropped -3.84% vs APOIX's -14.54%.

Which has better risk-adjusted returns?

APOIX currently has the higher Sharpe Ratio (2.45 vs 1.56), 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.