WBEIX vs. COBYX

Last updated Jun 23, 2026

WBEIX (William Blair Emerging Markets Growth Fund) and COBYX (The Cook & Bynum Fund) are both Emerging Markets Diversified funds. Over the past 10 years, WBEIX returned 11.79%/yr vs 4.64%/yr for COBYX. At a 0.39 correlation, their price movements are largely independent. WBEIX charges 1.11%/yr vs 1.49%/yr for COBYX.

Performance

WBEIX vs. COBYX - Performance Comparison

The chart below illustrates the hypothetical performance of a $10,000 investment in William Blair Emerging Markets Growth Fund (WBEIX) and The Cook & Bynum Fund (COBYX). The values are adjusted to include any dividend payments, if applicable.

Returns By Period

In the year-to-date period, WBEIX achieves a 38.55% return, which is significantly higher than COBYX's 9.37% return. Over the past 10 years, WBEIX has outperformed COBYX with an annualized return of 11.79%, while COBYX has yielded a comparatively lower 4.64% annualized return.

WBEIX

• 1D: 3.36%
• 1M: 8.00%
• YTD: 38.55%
• 6M: 41.11%
• 1Y: 65.43%
• 3Y*: 25.02%
• 5Y*: 6.26%
• 10Y*: 11.79%

COBYX

• 1D: -1.13%
• 1M: -1.99%
• YTD: 9.37%
• 6M: 9.19%
• 1Y: 14.99%
• 3Y*: 6.69%
• 5Y*: 8.29%
• 10Y*: 4.64%

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

WBEIX vs. COBYX - Yearly Performance Comparison

	2026 (YTD)	2025	2024	2023	2022	2021	2020	2019	2018	2017
WBEIX William Blair Emerging Markets Growth Fund	38.55%	25.18%	10.62%	10.23%	-33.15%	3.23%	40.77%	28.36%	-21.31%	48.82%
COBYX The Cook & Bynum Fund	9.37%	20.50%	-10.32%	16.73%	9.28%	9.05%	-10.97%	9.40%	-13.40%	15.12%

Correlation

The correlation between WBEIX and COBYX is 0.15, which is low. Their price movements are largely independent, making them effective diversification partners.

	Correlation
Correlation (1Y) Calculated over the trailing 1-year period	0.15
Correlation (3Y) Calculated over the trailing 3-year period	0.28
Correlation (5Y) Calculated over the trailing 5-year period	0.33
Correlation (10Y) Calculated over the trailing 10-year period	0.37
Correlation (All Time) Calculated using the full available price history since Jan 2, 2013	0.39

Over the past year, the correlation between WBEIX and COBYX has dropped to 0.15 - well below their long-term average of 0.39, suggesting their price drivers have been diverging.

Return for Risk

WBEIX vs. COBYX — Risk / Return Rank

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

WBEIX

WBEIX Risk / Return Rank: 88
WBEIX Sharpe Ratio Rank: 92
WBEIX Sortino Ratio Rank: 81
WBEIX Omega Ratio Rank: 84
WBEIX Calmar Ratio Rank: 92
WBEIX Martin Ratio Rank: 90

COBYX

COBYX Risk / Return Rank: 25
COBYX Sharpe Ratio Rank: 24
COBYX Sortino Ratio Rank: 26
COBYX Omega Ratio Rank: 23
COBYX Calmar Ratio Rank: 25
COBYX Martin Ratio Rank: 26

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.

WBEIX vs. COBYX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for William Blair Emerging Markets Growth Fund (WBEIX) and The Cook & Bynum Fund (COBYX). 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.

Values are calculated on a 1-year rolling basis and updated daily. Risk-adjusted metrics are more stable over longer periods — use the period switch above to explore them.

	WBEIX	COBYX	Difference
Sharpe ratio: Return per unit of total volatility	2.87	1.32	+1.55
Sortino ratio: Return per unit of downside risk	3.52	1.96	+1.55
Omega ratio: Gain probability vs. loss probability	1.52	1.24	+0.28
Calmar ratio: Return relative to maximum drawdown	4.68	1.75	+2.93
Martin ratio: Return relative to average drawdown	16.74	5.63	+11.11

WBEIX vs. COBYX - Sharpe Ratio Comparison

The current WBEIX Sharpe Ratio is 2.87, which is higher than the COBYX Sharpe Ratio of 1.32. The chart below compares the historical Sharpe Ratios of WBEIX and COBYX, calculated using daily returns over the previous 12 months. A higher Sharpe Ratio indicates better risk-adjusted performance relative to the risk-free rate.

Drawdowns

WBEIX vs. COBYX - Drawdown Comparison

The maximum WBEIX drawdown since its inception was -71.18%, which is greater than COBYX's maximum drawdown of -34.18%. Use the drawdown chart below to compare losses from any high point for WBEIX and COBYX.

Drawdown Indicators

	WBEIX	COBYX	Difference
Max Drawdown Largest peak-to-trough decline	-71.18%	-34.18%	-37.00%
Max Drawdown (1Y) Largest decline over 1 year	-14.04%	-8.95%	-5.09%
Max Drawdown (3Y) Largest decline over 3 years	-19.64%	-16.29%	-3.35%
Max Drawdown (5Y) Largest decline over 5 years	-40.95%	-17.10%	-23.85%
Max Drawdown (10Y) Largest decline over 10 years	-43.75%	-34.18%	-9.57%
Current Drawdown Current decline from peak	0.00%	-2.33%	+2.33%
Average Drawdown Average peak-to-trough decline	-21.42%	-6.78%	-14.64%
Ulcer Index Depth and duration of drawdowns from previous peaks	3.91%	2.79%	+1.12%

Volatility

WBEIX vs. COBYX - Volatility Comparison

William Blair Emerging Markets Growth Fund (WBEIX) has a higher volatility of 11.13% compared to The Cook & Bynum Fund (COBYX) at 3.04%. This indicates that WBEIX's price experiences larger fluctuations and is considered to be riskier than COBYX based on this measure. The chart below showcases a comparison of their rolling one-month volatility.

Volatility by Period

	WBEIX	COBYX	Difference
Volatility (1M) Calculated over the trailing 1-month period	11.13%	3.04%	+8.09%
Volatility (6M) Calculated over the trailing 6-month period	20.00%	9.54%	+10.46%
Volatility (1Y) Calculated over the trailing 1-year period	22.94%	11.90%	+11.04%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	17.31%	13.99%	+3.32%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	18.07%	13.65%	+4.42%

WBEIX vs. COBYX - Expense Ratio Comparison

WBEIX has a 1.11% expense ratio, which is lower than COBYX's 1.49% expense ratio.

Dividends

WBEIX vs. COBYX - Dividend Comparison

WBEIX's dividend yield for the trailing twelve months is around 0.29%, less than COBYX's 1.08% yield.

Position	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017	2016	2015
COBYX The Cook & Bynum Fund	1.08%	1.18%	0.00%	1.01%	1.16%	2.18%	0.32%	0.69%	12.60%	1.88%	5.09%	0.00%
WBEIX William Blair Emerging Markets Growth Fund	0.29%	0.41%	0.10%	0.53%	0.16%	21.21%	4.12%	4.31%	14.57%	0.94%	0.45%	1.11%

Frequently Asked Questions

Can I hold both WBEIX and COBYX in my portfolio?

WBEIX and COBYX have a correlation of 0.15, meaning they provide meaningful diversification benefit when combined. Depending on your allocation goals, holding both could reduce overall portfolio risk.

Which is riskier, WBEIX or COBYX?

WBEIX has higher volatility (11.13%) compared to COBYX (3.04%). In terms of maximum drawdown, WBEIX dropped -71.18% vs COBYX's -34.18%.

Which has better risk-adjusted returns?

WBEIX currently has the higher Sharpe Ratio (2.87 vs 1.32), 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.