APOIX vs. VTSPX

Last updated Jun 4, 2026

APOIX (American Century Short Duration Inflation Protection Bond Fund Investor Class) and VTSPX (Vanguard Short-Term Inflation-Protected Securities Index Fund Institutional Shares) are both Inflation-Protected Bonds funds. Over the past 10 years, APOIX returned 3.13%/yr vs 3.16%/yr for VTSPX. Their correlation of 0.88 suggests significant overlap in exposure. APOIX charges 0.57%/yr vs 0.04%/yr for VTSPX.

Performance

APOIX vs. VTSPX - Performance Comparison

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

Returns By Period

The year-to-date returns for both investments are quite close, with APOIX having a 2.02% return and VTSPX slightly higher at 2.06%. Both investments have delivered pretty close results over the past 10 years, with APOIX having a 3.13% annualized return and VTSPX not far ahead at 3.16%.

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%

VTSPX

• 1D: 0.00%
• 1M: 0.04%
• YTD: 2.06%
• 6M: 2.05%
• 1Y: 4.72%
• 3Y*: 5.26%
• 5Y*: 3.40%
• 10Y*: 3.16%

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

APOIX vs. VTSPX - Yearly Performance Comparison

	2026 (YTD)	2025	2024	2023	2022	2021	2020	2019	2018	2017
APOIX American Century Short Duration Inflation Protection Bond Fund Investor Class	2.02%	5.95%	4.15%	3.82%	-3.89%	6.30%	5.06%	4.77%	1.81%	0.73%
VTSPX Vanguard Short-Term Inflation-Protected Securities Index Fund Institutional Shares	2.06%	6.06%	4.75%	4.61%	-2.82%	5.32%	4.99%	4.82%	0.59%	0.83%

Correlation

The correlation between APOIX and VTSPX is 0.86, 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	0.86
Correlation (3Y) Calculated over the trailing 3-year period	0.91
Correlation (5Y) Calculated over the trailing 5-year period	0.92
Correlation (10Y) Calculated over the trailing 10-year period	0.88
Correlation (All Time) Calculated using the full available price history since Jan 3, 2013	0.88

The correlation between APOIX and VTSPX has been stable across timeframes, ranging from 0.86 to 0.92 - a consistent structural relationship.

Return for Risk

APOIX vs. VTSPX — Risk / Return Rank

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

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

VTSPX

VTSPX Risk / Return Rank: 94
VTSPX Sharpe Ratio Rank: 91
VTSPX Sortino Ratio Rank: 96
VTSPX Omega Ratio Rank: 91
VTSPX Calmar Ratio Rank: 96
VTSPX Martin Ratio Rank: 97

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.

APOIX vs. VTSPX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for American Century Short Duration Inflation Protection Bond Fund Investor Class (APOIX) and Vanguard Short-Term Inflation-Protected Securities Index Fund Institutional Shares (VTSPX). 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.

	APOIX	VTSPX	Difference
Sharpe ratio Return per unit of total volatility	2.45	3.06	-0.60
Sortino ratio Return per unit of downside risk	4.00	5.19	-1.19
Omega ratio Gain probability vs. loss probability	1.51	1.67	-0.16
Calmar ratio Return relative to maximum drawdown	5.81	6.50	-0.69
Martin ratio Return relative to average drawdown	19.09	25.54	-6.45
Data is calculated on a 1-year rolling basis and updated daily. The trend shows the change in the indicator over the past month.

APOIX vs. VTSPX - Sharpe Ratio Comparison

The current APOIX Sharpe Ratio is 2.45, which is comparable to the VTSPX Sharpe Ratio of 3.06. The chart below compares the historical Sharpe Ratios of APOIX and VTSPX, 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

	APOIX	VTSPX	Difference
Sharpe Ratio (1Y) Calculated over the trailing 1-year period	2.45	3.06	-0.60
Sharpe Ratio (5Y) Calculated over the trailing 5-year period	0.90	1.28	-0.38
Sharpe Ratio (10Y) Calculated over the trailing 10-year period	1.10	1.42	-0.32
Sharpe Ratio (All Time) Calculated using the full available price history	0.72	1.08	-0.37

Drawdowns

APOIX vs. VTSPX - Drawdown Comparison

The maximum APOIX drawdown since its inception was -14.54%, which is greater than VTSPX's maximum drawdown of -5.35%. Use the drawdown chart below to compare losses from any high point for APOIX and VTSPX.

Drawdown Indicators

	APOIX	VTSPX	Difference
Max Drawdown Largest peak-to-trough decline	-14.54%	-5.35%	-9.19%
Max Drawdown (1Y) Largest decline over 1 year	-0.76%	-0.72%	-0.04%
Max Drawdown (3Y) Largest decline over 3 years	-1.42%	-0.92%	-0.50%
Max Drawdown (5Y) Largest decline over 5 years	-6.58%	-5.35%	-1.23%
Max Drawdown (10Y) Largest decline over 10 years	-6.58%	-5.35%	-1.23%
Current Drawdown Current decline from peak	-0.00%	-0.04%	+0.04%
Average Drawdown Average peak-to-trough decline	-1.99%	-1.01%	-0.98%
Ulcer Index Depth and duration of drawdowns from previous peaks	0.23%	0.18%	+0.05%

Volatility

APOIX vs. VTSPX - Volatility Comparison

The current volatility for American Century Short Duration Inflation Protection Bond Fund Investor Class (APOIX) is 0.51%, while Vanguard Short-Term Inflation-Protected Securities Index Fund Institutional Shares (VTSPX) has a volatility of 0.57%. This indicates that APOIX experiences smaller price fluctuations and is considered to be less risky than VTSPX based on this measure. The chart below showcases a comparison of their rolling one-month volatility.

Volatility by Period

	APOIX	VTSPX	Difference
Volatility (1M) Calculated over the trailing 1-month period	0.51%	0.57%	-0.06%
Volatility (6M) Calculated over the trailing 6-month period	1.25%	1.12%	+0.13%
Volatility (1Y) Calculated over the trailing 1-year period	1.81%	1.52%	+0.29%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	3.31%	2.67%	+0.64%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	2.85%	2.23%	+0.62%

APOIX vs. VTSPX - Expense Ratio Comparison

APOIX has a 0.57% expense ratio, which is higher than VTSPX's 0.04% expense ratio.

Dividends

APOIX vs. VTSPX - Dividend Comparison

APOIX's dividend yield for the trailing twelve months is around 3.91%, more than VTSPX's 3.59% 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%
VTSPX Vanguard Short-Term Inflation-Protected Securities Index Fund Institutional Shares	3.59%	3.81%	2.70%	2.86%	6.84%	4.69%	1.21%	1.96%	2.47%	1.52%	0.80%

Frequently Asked Questions

Can I hold both APOIX and VTSPX in my portfolio?

APOIX and VTSPX have a correlation of 0.86, meaning they provide meaningful diversification benefit when combined. Depending on your allocation goals, holding both could reduce overall portfolio risk.

Which is riskier, APOIX or VTSPX?

VTSPX has higher volatility (0.57%) compared to APOIX (0.51%). In terms of maximum drawdown, APOIX dropped -14.54% vs VTSPX's -5.35%.

Which has better risk-adjusted returns?

VTSPX currently has the higher Sharpe Ratio (3.06 vs 2.45), 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.