WBSIX vs. NEAIX

Last updated Apr 1, 2026

Compare and contrast key facts about William Blair Small Cap Growth Fund (WBSIX) and Needham Aggressive Growth Fund Institutional Class (NEAIX).

WBSIX is managed by William Blair. It was launched on Dec 27, 1999. NEAIX is an actively managed fund by Needham. It was launched on Dec 30, 2016.

Performance

WBSIX vs. NEAIX - Performance Comparison

The chart below illustrates the hypothetical performance of a $10,000 investment in William Blair Small Cap Growth Fund (WBSIX) and Needham Aggressive Growth Fund Institutional Class (NEAIX). The values are adjusted to include any dividend payments, if applicable.

WBSIX vs. NEAIX - Yearly Performance Comparison

	2026 (YTD)	2025	2024	2023	2022	2021	2020	2019	2018	2017
WBSIX William Blair Small Cap Growth Fund	-5.23%	3.03%	32.88%	16.38%	-21.46%	12.64%	38.87%	22.53%	-2.08%	26.58%
NEAIX Needham Aggressive Growth Fund Institutional Class	7.37%	26.99%	14.86%	38.37%	-27.02%	38.46%	52.49%	44.68%	-15.64%	10.07%

Returns By Period

In the year-to-date period, WBSIX achieves a -5.23% return, which is significantly lower than NEAIX's 7.37% return.

WBSIX

• 1D: -1.26%
• 1M: -10.26%
• YTD: -5.23%
• 6M: -2.35%
• 1Y: 9.76%
• 3Y*: 12.31%
• 5Y*: 4.37%
• 10Y*: 13.07%

NEAIX

• 1D: -3.89%
• 1M: -9.47%
• YTD: 7.37%
• 6M: 10.73%
• 1Y: 55.63%
• 3Y*: 25.66%
• 5Y*: 15.35%
• 10Y*: —

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

WBSIX vs. NEAIX - Expense Ratio Comparison

WBSIX has a 1.25% expense ratio, which is higher than NEAIX's 1.20% expense ratio.

WBSIX

William Blair Small Cap Growth Fund

NEAIX

Needham Aggressive Growth Fund Institutional Class

Return for Risk

WBSIX vs. NEAIX — Risk / Return Rank

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

WBSIX

WBSIX Risk / Return Rank: 16
WBSIX Sharpe Ratio Rank: 15
WBSIX Sortino Ratio Rank: 17
WBSIX Omega Ratio Rank: 15
WBSIX Calmar Ratio Rank: 16
WBSIX Martin Ratio Rank: 16

NEAIX

NEAIX Risk / Return Rank: 91
NEAIX Sharpe Ratio Rank: 90
NEAIX Sortino Ratio Rank: 89
NEAIX Omega Ratio Rank: 84
NEAIX Calmar Ratio Rank: 96
NEAIX Martin Ratio Rank: 95

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. NEAIX - Risk-Adjusted Trends Comparison

This table presents a comparison of risk-adjusted performance metrics for William Blair Small Cap Growth Fund (WBSIX) and Needham Aggressive Growth Fund Institutional Class (NEAIX). 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	NEAIX	Difference
Sharpe ratio Return per unit of total volatility	0.40	1.89	-1.49
Sortino ratio Return per unit of downside risk	0.74	2.45	-1.71
Omega ratio Gain probability vs. loss probability	1.09	1.34	-0.25
Calmar ratio Return relative to maximum drawdown	0.45	3.57	-3.11
Martin ratio Return relative to average drawdown	1.56	12.81	-11.25
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. NEAIX - Sharpe Ratio Comparison

The current WBSIX Sharpe Ratio is 0.40, which is lower than the NEAIX Sharpe Ratio of 1.89. The chart below compares the historical Sharpe Ratios of WBSIX and NEAIX, offering insights into how both investments have performed under varying market conditions. These values are calculated using daily returns over the previous 12 months.

Sharpe Ratios by Period

	WBSIX	NEAIX	Difference
Sharpe Ratio (1Y) Calculated over the trailing 1-year period	0.40	1.89	-1.49
Sharpe Ratio (5Y) Calculated over the trailing 5-year period	0.18	0.64	-0.45
Sharpe Ratio (10Y) Calculated over the trailing 10-year period	0.57	—	—
Sharpe Ratio (All Time) Calculated using the full available price history	0.51	0.72	-0.21

Correlation

The correlation between WBSIX and NEAIX is 0.84, which is considered to be high. That indicates a strong positive relationship between their price movements. Having highly-correlated positions in a portfolio may signal a lack of diversification, potentially leading to increased risk during market downturns.

Dividends

WBSIX vs. NEAIX - Dividend Comparison

WBSIX's dividend yield for the trailing twelve months is around 7.90%, more than NEAIX's 1.88% yield.

	TTM	2025	2024	2023	2022	2021	2020	2019	2018	2017	2016	2015
WBSIX William Blair Small Cap Growth Fund	7.90%	7.49%	20.14%	1.53%	3.55%	17.85%	9.73%	2.07%	12.60%	16.89%	5.42%	8.25%
NEAIX Needham Aggressive Growth Fund Institutional Class	1.88%	2.01%	0.00%	0.00%	0.00%	6.84%	3.80%	10.42%	16.35%	5.14%	0.00%	0.00%

Drawdowns

WBSIX vs. NEAIX - Drawdown Comparison

The maximum WBSIX drawdown since its inception was -62.35%, which is greater than NEAIX's maximum drawdown of -35.93%. Use the drawdown chart below to compare losses from any high point for WBSIX and NEAIX.

Drawdown Indicators

	WBSIX	NEAIX	Difference
Max Drawdown Largest peak-to-trough decline	-62.35%	-35.93%	-26.42%
Max Drawdown (1Y) Largest decline over 1 year	-13.31%	-13.98%	+0.67%
Max Drawdown (5Y) Largest decline over 5 years	-38.13%	-35.93%	-2.20%
Max Drawdown (10Y) Largest decline over 10 years	-39.16%	—	—
Current Drawdown Current decline from peak	-12.75%	-11.55%	-1.20%
Average Drawdown Average peak-to-trough decline	-11.20%	-8.73%	-2.47%
Ulcer Index Depth and duration of drawdowns from previous peaks	4.02%	3.89%	+0.13%

Volatility

WBSIX vs. NEAIX - Volatility Comparison

The current volatility for William Blair Small Cap Growth Fund (WBSIX) is 6.91%, while Needham Aggressive Growth Fund Institutional Class (NEAIX) has a volatility of 10.98%. This indicates that WBSIX experiences smaller price fluctuations and is considered to be less risky than NEAIX based on this measure. The chart below showcases a comparison of their rolling one-month volatility.

Volatility by Period

	WBSIX	NEAIX	Difference
Volatility (1M) Calculated over the trailing 1-month period	6.91%	10.98%	-4.07%
Volatility (6M) Calculated over the trailing 6-month period	14.89%	19.41%	-4.52%
Volatility (1Y) Calculated over the trailing 1-year period	23.53%	28.68%	-5.15%
Volatility (5Y) Calculated over the trailing 5-year period, annualized	23.78%	24.28%	-0.50%
Volatility (10Y) Calculated over the trailing 10-year period, annualized	22.91%	24.42%	-1.51%