WBSIX vs. WBIIX

Last updated Jun 3, 2026

WBSIX (William Blair Small Cap Growth Fund) and WBIIX (William Blair Institutional International Growth Fund) are both mutual funds - WBSIX is a Small Cap Growth Equities fund managed by William Blair, while WBIIX is a Foreign Large Cap Equities fund managed by William Blair. Over the past 10 years, WBSIX returned 14.65%/yr vs 8.63%/yr for WBIIX. A 0.65 correlation means they provide meaningful diversification when combined. WBSIX charges 1.25%/yr vs 0.98%/yr for WBIIX.

Performance

WBSIX vs. WBIIX - Performance Comparison

The chart below illustrates the hypothetical performance of a $10,000 investment in William Blair Small Cap Growth Fund (WBSIX) and William Blair Institutional International Growth Fund (WBIIX). 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 WBSIX having a 14.56% return and WBIIX slightly higher at 14.90%. Over the past 10 years, WBSIX has outperformed WBIIX with an annualized return of 14.65%, while WBIIX has yielded a comparatively lower 8.63% annualized return.

WBSIX

• 1D: -0.03%
• 1M: 3.44%
• YTD: 14.56%
• 6M: 16.81%
• 1Y: 31.17%
• 3Y*: 19.11%
• 5Y*: 7.93%
• 10Y*: 14.65%

WBIIX

• 1D: -0.48%
• 1M: 5.97%
• YTD: 14.90%
• 6M: 17.75%
• 1Y: 23.12%
• 3Y*: 13.33%
• 5Y*: 3.04%
• 10Y*: 8.63%

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

WBSIX vs. WBIIX - Yearly Performance Comparison

	2026 (YTD)	2025	2024	2023	2022	2021	2020	2019	2018	2017
WBSIX William Blair Small Cap Growth Fund	14.56%	3.03%	32.88%	16.38%	-21.46%	12.64%	38.87%	22.53%	-2.08%	26.81%
WBIIX William Blair Institutional International Growth Fund	14.90%	18.16%	2.40%	15.23%	-28.39%	9.30%	32.69%	30.75%	-17.49%	29.51%

Correlation

The correlation between WBSIX and WBIIX is 0.56, 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	0.56
Correlation (3Y) Calculated over the trailing 3-year period	0.62
Correlation (5Y) Calculated over the trailing 5-year period	0.66
Correlation (10Y) Calculated over the trailing 10-year period	0.62
Correlation (All Time) Calculated using the full available price history since Jul 30, 2002	0.65

The correlation between WBSIX and WBIIX has been stable across timeframes, ranging from 0.56 to 0.66 - a consistent structural relationship.

Return for Risk

WBSIX vs. WBIIX — Risk / Return Rank

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

WBSIX

WBSIX Risk / Return Rank: 35
WBSIX Sharpe Ratio Rank: 31
WBSIX Sortino Ratio Rank: 31
WBSIX Omega Ratio Rank: 27
WBSIX Calmar Ratio Rank: 42
WBSIX Martin Ratio Rank: 42

WBIIX

WBIIX Risk / Return Rank: 29
WBIIX Sharpe Ratio Rank: 31
WBIIX Sortino Ratio Rank: 29
WBIIX Omega Ratio Rank: 34
WBIIX Calmar Ratio Rank: 22
WBIIX Martin Ratio Rank: 28

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.

WBSIX vs. WBIIX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for William Blair Small Cap Growth Fund (WBSIX) and William Blair Institutional International Growth Fund (WBIIX). 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.

	WBSIX	WBIIX	Difference
Sharpe ratio Return per unit of total volatility	1.62	1.59	+0.03
Sortino ratio Return per unit of downside risk	2.34	2.23	+0.11
Omega ratio Gain probability vs. loss probability	1.27	1.31	-0.04
Calmar ratio Return relative to maximum drawdown	2.51	1.78	+0.73
Martin ratio Return relative to average drawdown	9.11	6.73	+2.38
Data is calculated on a 1-year rolling basis and updated daily. The trend shows the change in the indicator over the past month.

WBSIX vs. WBIIX - Sharpe Ratio Comparison

The current WBSIX Sharpe Ratio is 1.62, which is comparable to the WBIIX Sharpe Ratio of 1.59. The chart below compares the historical Sharpe Ratios of WBSIX and WBIIX, 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

	WBSIX	WBIIX	Difference
Sharpe Ratio (1Y) Calculated over the trailing 1-year period	1.62	1.59	+0.03
Sharpe Ratio (5Y) Calculated over the trailing 5-year period	0.33	0.18	+0.15
Sharpe Ratio (10Y) Calculated over the trailing 10-year period	0.64	0.50	+0.13
Sharpe Ratio (All Time) Calculated using the full available price history	0.54	0.44	+0.10

Drawdowns

WBSIX vs. WBIIX - Drawdown Comparison

The maximum WBSIX drawdown since its inception was -62.35%, roughly equal to the maximum WBIIX drawdown of -65.13%. Use the drawdown chart below to compare losses from any high point for WBSIX and WBIIX.

Drawdown Indicators

	WBSIX	WBIIX	Difference
Max Drawdown Largest peak-to-trough decline	-62.35%	-65.13%	+2.78%
Max Drawdown (1Y) Largest decline over 1 year	-12.75%	-13.17%	+0.42%
Max Drawdown (3Y) Largest decline over 3 years	-24.76%	-17.06%	-7.70%
Max Drawdown (5Y) Largest decline over 5 years	-38.13%	-40.91%	+2.78%
Max Drawdown (10Y) Largest decline over 10 years	-39.16%	-40.91%	+1.75%
Current Drawdown Current decline from peak	-0.59%	-0.48%	-0.11%
Average Drawdown Average peak-to-trough decline	-11.14%	-14.80%	+3.66%
Ulcer Index Depth and duration of drawdowns from previous peaks	3.51%	3.48%	+0.03%

Volatility

WBSIX vs. WBIIX - Volatility Comparison

William Blair Small Cap Growth Fund (WBSIX) and William Blair Institutional International Growth Fund (WBIIX) have volatilities of 5.50% and 5.45%, 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

	WBSIX	WBIIX	Difference
Volatility (1M) Calculated over the trailing 1-month period	5.50%	5.45%	+0.05%
Volatility (6M) Calculated over the trailing 6-month period	14.42%	12.69%	+1.73%
Volatility (1Y) Calculated over the trailing 1-year period	19.99%	15.00%	+4.99%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	23.85%	16.66%	+7.19%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	23.02%	17.18%	+5.84%

WBSIX vs. WBIIX - Expense Ratio Comparison

WBSIX has a 1.25% expense ratio, which is higher than WBIIX's 0.98% expense ratio.

Dividends

WBSIX vs. WBIIX - Dividend Comparison

WBSIX's dividend yield for the trailing twelve months is around 6.54%, less than WBIIX's 10.90% yield.

Position	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017	2016	2015
WBIIX William Blair Institutional International Growth Fund	10.90%	12.53%	7.49%	2.51%	6.57%	16.58%	12.61%	0.95%	11.74%	4.16%	1.15%	1.28%
WBSIX William Blair Small Cap Growth Fund	6.54%	7.49%	20.14%	1.53%	3.55%	17.85%	9.73%	2.07%	12.60%	16.89%	5.42%	8.25%

Frequently Asked Questions

Can I hold both WBSIX and WBIIX in my portfolio?

WBSIX and WBIIX have a correlation of 0.56, meaning they provide meaningful diversification benefit when combined. Depending on your allocation goals, holding both could reduce overall portfolio risk.

Which is riskier, WBSIX or WBIIX?

WBSIX has higher volatility (5.50%) compared to WBIIX (5.45%). In terms of maximum drawdown, WBSIX dropped -62.35% vs WBIIX's -65.13%.

Which has better risk-adjusted returns?

WBSIX currently has the higher Sharpe Ratio (1.62 vs 1.59), 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.