WBIGX vs. FSOSX

Last updated Jun 4, 2026

WBIGX (William Blair International Growth Fund) and FSOSX (Fidelity Series Overseas Fund) are both Foreign Large Cap Equities funds. Over the past 5 years, WBIGX returned 3.08%/yr vs 6.73%/yr for FSOSX. Their correlation of 0.90 suggests significant overlap in exposure. WBIGX charges 1.31%/yr vs 0.01%/yr for FSOSX.

Performance

WBIGX vs. FSOSX - Performance Comparison

The chart below illustrates the hypothetical performance of a $10,000 investment in William Blair International Growth Fund (WBIGX) and Fidelity Series Overseas Fund (FSOSX). The values are adjusted to include any dividend payments, if applicable.

Returns By Period

In the year-to-date period, WBIGX achieves a 15.58% return, which is significantly higher than FSOSX's 5.63% return.

WBIGX

• 1D: 0.64%
• 1M: 6.37%
• YTD: 15.58%
• 6M: 18.00%
• 1Y: 24.16%
• 3Y*: 13.39%
• 5Y*: 3.08%
• 10Y*: 8.28%

FSOSX

• 1D: 0.96%
• 1M: 3.89%
• YTD: 5.63%
• 6M: 7.55%
• 1Y: 8.98%
• 3Y*: 13.16%
• 5Y*: 6.73%
• 10Y*: —

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

WBIGX vs. FSOSX - Yearly Performance Comparison

	2026 (YTD)	2025	2024	2023	2022	2021	2020	2019
WBIGX William Blair International Growth Fund	15.58%	17.90%	2.11%	15.16%	-28.65%	8.61%	31.66%	9.20%
FSOSX Fidelity Series Overseas Fund	5.63%	21.29%	5.87%	21.49%	-23.25%	19.59%	16.36%	7.78%

Correlation

The correlation between WBIGX and FSOSX is 0.79, 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	0.79
Correlation (3Y) Calculated over the trailing 3-year period	0.86
Correlation (5Y) Calculated over the trailing 5-year period	0.90
Correlation (All Time) Calculated using the full available price history since Jul 1, 2019	0.90

The correlation between WBIGX and FSOSX shifts across timeframes, from 0.79 (1 year) to 0.90 (5 years), reflecting how their relationship changes across market environments.

Return for Risk

WBIGX vs. FSOSX — Risk / Return Rank

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

WBIGX

WBIGX Risk / Return Rank: 29
WBIGX Sharpe Ratio Rank: 31
WBIGX Sortino Ratio Rank: 29
WBIGX Omega Ratio Rank: 34
WBIGX Calmar Ratio Rank: 24
WBIGX Martin Ratio Rank: 29

FSOSX

FSOSX Risk / Return Rank: 7
FSOSX Sharpe Ratio Rank: 6
FSOSX Sortino Ratio Rank: 6
FSOSX Omega Ratio Rank: 6
FSOSX Calmar Ratio Rank: 7
FSOSX Martin Ratio Rank: 8

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.

WBIGX vs. FSOSX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for William Blair International Growth Fund (WBIGX) and Fidelity Series Overseas Fund (FSOSX). 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.

	WBIGX	FSOSX	Difference
Sharpe ratio Return per unit of total volatility	1.59	0.50	+1.09
Sortino ratio Return per unit of downside risk	2.23	0.83	+1.40
Omega ratio Gain probability vs. loss probability	1.31	1.10	+0.21
Calmar ratio Return relative to maximum drawdown	1.81	0.68	+1.13
Martin ratio Return relative to average drawdown	6.80	2.42	+4.38
Data is calculated on a 1-year rolling basis and updated daily. The trend shows the change in the indicator over the past month.

WBIGX vs. FSOSX - Sharpe Ratio Comparison

The current WBIGX Sharpe Ratio is 1.59, which is higher than the FSOSX Sharpe Ratio of 0.50. The chart below compares the historical Sharpe Ratios of WBIGX and FSOSX, 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

	WBIGX	FSOSX	Difference
Sharpe Ratio (1Y) Calculated over the trailing 1-year period	1.59	0.50	+1.09
Sharpe Ratio (5Y) Calculated over the trailing 5-year period	0.19	0.38	-0.20
Sharpe Ratio (10Y) Calculated over the trailing 10-year period	0.48	—	—
Sharpe Ratio (All Time) Calculated using the full available price history	0.51	0.51	0.00

Drawdowns

WBIGX vs. FSOSX - Drawdown Comparison

The maximum WBIGX drawdown since its inception was -65.35%, which is greater than FSOSX's maximum drawdown of -35.36%. Use the drawdown chart below to compare losses from any high point for WBIGX and FSOSX.

Drawdown Indicators

	WBIGX	FSOSX	Difference
Max Drawdown Largest peak-to-trough decline	-65.35%	-35.36%	-29.99%
Max Drawdown (1Y) Largest decline over 1 year	-13.23%	-12.39%	-0.84%
Max Drawdown (3Y) Largest decline over 3 years	-17.22%	-14.07%	-3.15%
Max Drawdown (5Y) Largest decline over 5 years	-41.18%	-35.36%	-5.82%
Max Drawdown (10Y) Largest decline over 10 years	-41.18%	—	—
Current Drawdown Current decline from peak	0.00%	-1.31%	+1.31%
Average Drawdown Average peak-to-trough decline	-14.76%	-7.78%	-6.98%
Ulcer Index Depth and duration of drawdowns from previous peaks	3.51%	3.46%	+0.05%

Volatility

WBIGX vs. FSOSX - Volatility Comparison

The current volatility for William Blair International Growth Fund (WBIGX) is 5.43%, while Fidelity Series Overseas Fund (FSOSX) has a volatility of 6.14%. This indicates that WBIGX experiences smaller price fluctuations and is considered to be less risky than FSOSX based on this measure. The chart below showcases a comparison of their rolling one-month volatility.

Volatility by Period

	WBIGX	FSOSX	Difference
Volatility (1M) Calculated over the trailing 1-month period	5.43%	6.14%	-0.71%
Volatility (6M) Calculated over the trailing 6-month period	12.75%	14.30%	-1.55%
Volatility (1Y) Calculated over the trailing 1-year period	15.07%	16.80%	-1.73%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	16.69%	17.67%	-0.98%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	17.23%	19.05%	-1.82%

WBIGX vs. FSOSX - Expense Ratio Comparison

WBIGX has a 1.31% expense ratio, which is higher than FSOSX's 0.01% expense ratio.

Dividends

WBIGX vs. FSOSX - Dividend Comparison

WBIGX's dividend yield for the trailing twelve months is around 16.41%, more than FSOSX's 8.66% yield.

Position	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017	2016	2015
FSOSX Fidelity Series Overseas Fund	8.66%	9.15%	2.25%	1.63%	1.80%	2.92%	1.12%	0.37%	0.00%	0.00%	0.00%	0.00%
WBIGX William Blair International Growth Fund	16.41%	18.97%	7.47%	3.38%	7.92%	11.75%	0.82%	1.07%	8.56%	1.28%	1.51%	0.92%

Frequently Asked Questions

Can I hold both WBIGX and FSOSX in my portfolio?

WBIGX and FSOSX have a correlation of 0.79, meaning they provide meaningful diversification benefit when combined. Depending on your allocation goals, holding both could reduce overall portfolio risk.

Which is riskier, WBIGX or FSOSX?

FSOSX has higher volatility (6.14%) compared to WBIGX (5.43%). In terms of maximum drawdown, WBIGX dropped -65.35% vs FSOSX's -35.36%.

Which has better risk-adjusted returns?

WBIGX currently has the higher Sharpe Ratio (1.59 vs 0.50), 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.