WBSIX Performance — William Blair Small Cap Growth Fund, Class I
Data updated: 2026-08-14
WBSIX returned +22.26% year to date and +32.95% over one year to Jun 2026. Annualised returns are +16.26% over 3 years and +6.61% over 5 years. The fund beat its US Small Growth category average: $100 invested three years ago grew to $157, against $156 for the category, and to $133 over one year, against $132. Volatility over the past three years was 19.34% a year. In the 12 months to Jun 2026 the fund took in a net $96.3M, and assets reached $1.22B.
WBSIX Growth of $100
What $100 invested in William Blair Small Cap Growth Fund grew to, compounded from monthly returns reported on SEC Form N-PORT, against the US Small Growth category average over the same months.
| Period | WBSIX | Category average |
|---|---|---|
| 1 year (Jul 2025 – Jun 2026) | $133 | $132 |
| 3 years (Jul 2023 – Jun 2026) | $157 | $156 |
| 5 years (Jul 2021 – Jun 2026) | $138 | $127 |
| Since data start (Jul 2019 – Jun 2026) | $222 | $203 |
WBSIX Trailing Returns
Total returns to Jun 2026, from SEC N-PORT.
| Period | Total return |
|---|---|
| YTD | +22.26% |
| 1 year | +32.95% |
| 3 years (annualised) | +16.26% |
| 5 years (annualised) | +6.61% |
WBSIX Annual Returns
Calendar-year total returns of William Blair Small Cap Growth Fund, compounded from monthly SEC N-PORT returns. Partial years show the months covered.
| Year | Total return |
|---|---|
| 2026 (Jan–Jun) | +22.26% |
| 2025 | +3.02% |
| 2024 | +19.33% |
| 2023 | +16.35% |
| 2022 | −21.39% |
| 2021 | +13.23% |
| 2020 | +38.66% |
| 2019 (Jul–Dec) | +2.85% |
WBSIX Monthly Returns
Monthly total returns as reported on SEC Form N-PORT.
| Year | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 2026 | +4.3% | +1.2% | −6.9% | +12.5% | +3.7% | +6.7% | — | — | — | — | — | — |
| 2025 | +2.6% | −5.9% | −7.8% | −2.9% | +3.5% | +5.9% | +0.4% | +6.0% | −0.8% | −0.8% | +3.4% | +0.4% |
| 2024 | −4.1% | +9.0% | +2.1% | −6.0% | +7.3% | +0.1% | +5.9% | −0.3% | +0.6% | −2.9% | +12.2% | −4.3% |
| 2023 | +10.3% | −1.5% | −1.9% | −1.5% | −0.9% | +7.0% | +3.1% | −4.3% | −4.7% | −6.9% | +8.4% | +10.1% |
| 2022 | −12.4% | +1.1% | +2.4% | −11.8% | −2.5% | −7.4% | +10.1% | −1.8% | −7.0% | +8.9% | +4.9% | −5.0% |
| 2021 | +1.5% | +7.0% | −0.7% | +3.5% | −1.7% | +2.9% | −1.4% | +4.2% | −2.5% | +5.4% | −5.3% | +0.3% |
| 2020 | +0.2% | −5.9% | −20.4% | +13.6% | +9.9% | +3.8% | +5.5% | +6.8% | −2.5% | +1.6% | +17.2% | +9.0% |
| 2019 | — | — | — | — | — | — | +0.7% | −2.3% | −1.2% | −0.1% | +5.1% | +0.8% |
WBSIX Risk
Risk measures from monthly returns over Jul 2023 – Jun 2026.
- 3-year volatility (annualised): 19.34%
- 3-year Sharpe ratio: 0.61 (vs 4.5% risk-free rate)
- Best month: +12.47% (Apr 2026)
- Worst month: −7.83% (Mar 2025)
WBSIX Fund Flows
Monthly money in and out of William Blair Small Cap Growth Fund, from SEC Form N-PORT.
- 12-month net flow: $96.3M
- 12-month gross sales (incl. reinvestments): $425.5M
- Sales ÷ redemptions: 1.29×
| Month | Sales | Redemptions | Net flow |
|---|---|---|---|
| Jun 2026 | $15.0M | $33.3M | −$18.3M |
| May 2026 | $23.6M | $30.1M | −$6.5M |
| Apr 2026 | $37.3M | $21.7M | $15.6M |
| Mar 2026 | $27.4M | $16.4M | $10.9M |
| Feb 2026 | $16.1M | $19.4M | −$3.3M |
| Jan 2026 | $50.5M | $35.6M | $14.9M |
| Dec 2025 | $89.4M | $49.2M | $40.2M |
| Nov 2025 | $10.8M | $35.8M | −$25.0M |
| Oct 2025 | $83.8M | $36.8M | $47.0M |
| Sep 2025 | $36.3M | $15.7M | $20.6M |
| Aug 2025 | $12.7M | $15.8M | −$3.1M |
| Jul 2025 | $22.5M | $19.3M | $3.2M |
WBSIX Assets Under Management
Net assets of William Blair Small Cap Growth Fund by report date, from SEC N-PORT filings.
| Report date | Net assets |
|---|---|
| 2026-06-30 | $1.22B |
| 2026-03-31 | $992.29M |
| 2025-12-31 | $987.51M |
| 2025-09-30 | $968.00M |
| 2025-06-30 | $897.29M |
| 2025-03-31 | $854.13M |
| 2024-12-31 | $924.75M |
| 2024-09-30 | $883.78M |
| 2024-06-30 | $822.51M |
| 2024-03-31 | $812.84M |
| 2023-12-31 | $747.26M |
| 2023-09-30 | $653.58M |
For information only. Not investment advice: figures are as reported in SEC filings and may contain errors or be out of date. Past performance does not guarantee future results.