AIOIX vs. VFSNX

Last updated Jun 4, 2026

AIOIX (American Century International Opportunities Fund) and VFSNX (Vanguard FTSE All-World ex-US Small-Cap Index Fund Institutional Shares) are both Foreign Small & Mid Cap Equities funds. Over the past 10 years, AIOIX returned 8.30%/yr vs 8.21%/yr for VFSNX. Their correlation of 0.91 suggests significant overlap in exposure. AIOIX charges 1.48%/yr vs 0.11%/yr for VFSNX.

Performance

AIOIX vs. VFSNX - Performance Comparison

The chart below illustrates the hypothetical performance of a $10,000 investment in American Century International Opportunities Fund (AIOIX) and Vanguard FTSE All-World ex-US Small-Cap Index Fund Institutional Shares (VFSNX). The values are adjusted to include any dividend payments, if applicable.

Returns By Period

In the year-to-date period, AIOIX achieves a 15.88% return, which is significantly higher than VFSNX's 11.76% return. Both investments have delivered pretty close results over the past 10 years, with AIOIX having a 8.30% annualized return and VFSNX not far behind at 8.21%.

AIOIX

• 1D: -0.15%
• 1M: 2.46%
• YTD: 15.88%
• 6M: 18.09%
• 1Y: 32.80%
• 3Y*: 15.62%
• 5Y*: 2.92%
• 10Y*: 8.30%

VFSNX

• 1D: 0.05%
• 1M: 1.81%
• YTD: 11.76%
• 6M: 14.55%
• 1Y: 28.61%
• 3Y*: 17.18%
• 5Y*: 6.19%
• 10Y*: 8.21%

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

AIOIX vs. VFSNX - Yearly Performance Comparison

	2026 (YTD)	2025	2024	2023	2022	2021	2020	2019	2018	2017
AIOIX American Century International Opportunities Fund	15.88%	29.62%	1.31%	8.63%	-30.19%	5.79%	31.07%	28.95%	-22.19%	45.09%
VFSNX Vanguard FTSE All-World ex-US Small-Cap Index Fund Institutional Shares	11.76%	29.97%	2.63%	15.18%	-21.26%	12.74%	11.92%	21.72%	-18.46%	30.30%

Correlation

The correlation between AIOIX and VFSNX 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 (3Y) Calculated over the trailing 3-year period	0.93
Correlation (5Y) Calculated over the trailing 5-year period	0.95
Correlation (10Y) Calculated over the trailing 10-year period	0.93
Correlation (All Time) Calculated using the full available price history since Mar 23, 2009	0.91

The correlation between AIOIX and VFSNX has been stable across timeframes, ranging from 0.91 to 0.95 - a consistent structural relationship.

Return for Risk

AIOIX vs. VFSNX — Risk / Return Rank

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

AIOIX

AIOIX Risk / Return Rank: 37
AIOIX Sharpe Ratio Rank: 35
AIOIX Sortino Ratio Rank: 32
AIOIX Omega Ratio Rank: 34
AIOIX Calmar Ratio Rank: 37
AIOIX Martin Ratio Rank: 44

VFSNX

VFSNX Risk / Return Rank: 47
VFSNX Sharpe Ratio Rank: 51
VFSNX Sortino Ratio Rank: 47
VFSNX Omega Ratio Rank: 50
VFSNX Calmar Ratio Rank: 42
VFSNX Martin Ratio Rank: 45

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.

AIOIX vs. VFSNX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for American Century International Opportunities Fund (AIOIX) and Vanguard FTSE All-World ex-US Small-Cap Index Fund Institutional Shares (VFSNX). 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.

	AIOIX	VFSNX	Difference
Sharpe ratio: Return per unit of total volatility	1.73	2.11	-0.39
Sortino ratio: Return per unit of downside risk	2.36	2.89	-0.52
Omega ratio: Gain probability vs. loss probability	1.31	1.39	-0.08
Calmar ratio: Return relative to maximum drawdown	2.32	2.46	-0.14
Martin ratio: Return relative to average drawdown	9.33	9.47	-0.14
Data is calculated on a 1-year rolling basis and updated daily. The trend shows the change in the indicator over the past month.

AIOIX vs. VFSNX - Sharpe Ratio Comparison

The current AIOIX Sharpe Ratio is 1.73, which is comparable to the VFSNX Sharpe Ratio of 2.11. The chart below compares the historical Sharpe Ratios of AIOIX and VFSNX, 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

	AIOIX	VFSNX	Difference
Sharpe Ratio (1Y) Calculated over the trailing 1-year period	1.73	2.11	-0.39
Sharpe Ratio (5Y) Calculated over the trailing 5-year period	0.16	0.41	-0.26
Sharpe Ratio (10Y) Calculated over the trailing 10-year period	0.44	0.52	-0.08
Sharpe Ratio (All Time) Calculated using the full available price history	0.55	0.59	-0.04

Drawdowns

AIOIX vs. VFSNX - Drawdown Comparison

The maximum AIOIX drawdown since its inception was -66.16%, which is greater than VFSNX's maximum drawdown of -43.65%. Use the drawdown chart below to compare losses from any high point for AIOIX and VFSNX.

Drawdown Indicators

	AIOIX	VFSNX	Difference
Max Drawdown Largest peak-to-trough decline	-66.16%	-43.65%	-22.51%
Max Drawdown (1Y) Largest decline over 1 year	-14.00%	-11.47%	-2.53%
Max Drawdown (3Y) Largest decline over 3 years	-18.46%	-14.70%	-3.76%
Max Drawdown (5Y) Largest decline over 5 years	-41.19%	-33.75%	-7.44%
Max Drawdown (10Y) Largest decline over 10 years	-41.19%	-43.65%	+2.46%
Current Drawdown Current decline from peak	-1.86%	-1.09%	-0.77%
Average Drawdown Average peak-to-trough decline	-16.02%	-9.49%	-6.53%
Ulcer Index Depth and duration of drawdowns from previous peaks	3.47%	2.98%	+0.49%

Volatility

AIOIX vs. VFSNX - Volatility Comparison

American Century International Opportunities Fund (AIOIX) has a higher volatility of 6.73% compared to Vanguard FTSE All-World ex-US Small-Cap Index Fund Institutional Shares (VFSNX) at 4.30%. This indicates that AIOIX's price experiences larger fluctuations and is considered to be riskier than VFSNX based on this measure. The chart below showcases a comparison of their rolling one-month volatility.

Volatility by Period

	AIOIX	VFSNX	Difference
Volatility (1M) Calculated over the trailing 1-month period	6.73%	4.30%	+2.43%
Volatility (6M) Calculated over the trailing 6-month period	16.02%	11.19%	+4.83%
Volatility (1Y) Calculated over the trailing 1-year period	18.86%	13.40%	+5.46%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	18.91%	15.03%	+3.88%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	18.95%	15.76%	+3.19%

AIOIX vs. VFSNX - Expense Ratio Comparison

AIOIX has a 1.48% expense ratio, which is higher than VFSNX's 0.11% expense ratio.

Dividends

AIOIX vs. VFSNX - Dividend Comparison

AIOIX's dividend yield for the trailing twelve months is around 0.24%, less than VFSNX's 3.01% yield.

Position	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017	2016	2015
AIOIX American Century International Opportunities Fund	0.24%	0.27%	0.32%	0.23%	0.00%	17.80%	3.18%	0.92%	5.28%	9.09%	0.04%	7.15%
VFSNX Vanguard FTSE All-World ex-US Small-Cap Index Fund Institutional Shares	3.01%	3.36%	3.41%	3.11%	2.26%	2.70%	1.90%	3.25%	2.81%	2.85%	2.93%	2.69%

Frequently Asked Questions

Can I hold both AIOIX and VFSNX in my portfolio?

With a correlation of 0.93, AIOIX and VFSNX 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, AIOIX or VFSNX?

AIOIX has higher volatility (6.73%) compared to VFSNX (4.30%). In terms of maximum drawdown, AIOIX dropped -66.16% vs VFSNX's -43.65%.

Which has better risk-adjusted returns?

VFSNX currently has the higher Sharpe Ratio (2.11 vs 1.73), 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.