WBIIX Performance — William Blair Institutional International Growth Fund, Institutional Class
Data updated: 2026-08-14
WBIIX returned +16.66% year to date and +21.72% over one year to Jun 2026. Annualised returns are +13.43% over 3 years and +3.27% over 5 years. The fund beat its International Large Growth category average: $100 invested three years ago grew to $146, against $139 for the category, and to $122 over one year, against $113. Volatility over the past three years was 15.34% a year. In the 12 months to Jun 2026 the fund lost a net $253.6M, and assets reached $779.77M.
WBIIX Growth of $100
What $100 invested in William Blair Institutional International Growth Fund grew to, compounded from monthly returns reported on SEC Form N-PORT, against the International Large Growth category average over the same months.
| Period | WBIIX | Category average |
|---|---|---|
| 1 year (Jul 2025 – Jun 2026) | $122 | $113 |
| 3 years (Jul 2023 – Jun 2026) | $146 | $139 |
| 5 years (Jul 2021 – Jun 2026) | $117 | $118 |
| Since data start (Jul 2019 – Jun 2026) | $185 | $178 |
WBIIX Trailing Returns
Total returns to Jun 2026, from SEC N-PORT.
| Period | Total return |
|---|---|
| YTD | +16.66% |
| 1 year | +21.72% |
| 3 years (annualised) | +13.43% |
| 5 years (annualised) | +3.27% |
WBIIX Annual Returns
Calendar-year total returns of William Blair Institutional International Growth Fund, compounded from monthly SEC N-PORT returns. Partial years show the months covered.
| Year | Total return |
|---|---|
| 2026 (Jan–Jun) | +16.66% |
| 2025 | +18.04% |
| 2024 | +2.42% |
| 2023 | +15.20% |
| 2022 | −28.28% |
| 2021 | +9.39% |
| 2020 | +32.46% |
| 2019 (Jul–Dec) | +9.50% |
WBIIX 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 | +5.7% | +4.7% | −10.3% | +9.5% | +6.2% | +1.0% | — | — | — | — | — | — |
| 2025 | +3.4% | −0.6% | −2.6% | +4.1% | +5.4% | +3.0% | −2.1% | +1.4% | +3.2% | +1.7% | −2.2% | +2.4% |
| 2024 | −0.8% | +4.7% | +2.5% | −5.5% | +3.7% | +0.2% | +1.9% | +2.5% | +0.2% | −4.3% | +0.1% | −2.3% |
| 2023 | +7.9% | −3.0% | +3.6% | +0.9% | −1.6% | +3.3% | +1.0% | −4.6% | −5.5% | −3.9% | +11.2% | +6.3% |
| 2022 | −11.4% | −4.4% | −0.5% | −9.2% | −1.2% | −8.3% | +8.9% | −6.1% | −10.2% | +6.5% | +10.3% | −4.2% |
| 2021 | +0.1% | 0.0% | −1.3% | +6.3% | +2.4% | +0.9% | +1.7% | +3.6% | −5.7% | +3.9% | −3.9% | +1.7% |
| 2020 | −0.8% | −6.0% | −13.9% | +9.4% | +8.7% | +5.5% | +7.4% | +6.2% | −0.9% | −1.2% | +10.7% | +6.5% |
| 2019 | — | — | — | — | — | — | −1.2% | −0.8% | +0.8% | +3.9% | +2.6% | +4.0% |
WBIIX Risk
Risk measures from monthly returns over Jul 2023 – Jun 2026.
- 3-year volatility (annualised): 15.34%
- 3-year Sharpe ratio: 0.58 (vs 4.5% risk-free rate)
- Best month: +11.21% (Nov 2023)
- Worst month: −10.31% (Mar 2026)
WBIIX Fund Flows
Monthly money in and out of William Blair Institutional International Growth Fund, from SEC Form N-PORT.
- 12-month net flow: −$253.6M
- 12-month gross sales (incl. reinvestments): $148.4M
- Sales ÷ redemptions: 0.37×
| Month | Sales | Redemptions | Net flow |
|---|---|---|---|
| Jun 2026 | $20.6M | $17.9M | $2.7M |
| May 2026 | $406K | $38.3M | −$37.9M |
| Apr 2026 | $314K | $34.4M | −$34.1M |
| Mar 2026 | $513K | $1.7M | −$1.1M |
| Feb 2026 | $13.1M | $16.8M | −$3.6M |
| Jan 2026 | $998K | $103.4M | −$102.4M |
| Dec 2025 | $102.9M | $142.5M | −$39.6M |
| Nov 2025 | $330K | $1.9M | −$1.6M |
| Oct 2025 | $5.7M | $11.7M | −$6.0M |
| Sep 2025 | $627K | $2.0M | −$1.4M |
| Aug 2025 | $422K | $2.0M | −$1.6M |
| Jul 2025 | $2.4M | $29.3M | −$26.9M |
WBIIX Assets Under Management
Net assets of William Blair Institutional International Growth Fund by report date, from SEC N-PORT filings.
| Report date | Net assets |
|---|---|
| 2026-06-30 | $779.77M |
| 2026-03-31 | $726.45M |
| 2025-12-31 | $834.52M |
| 2025-09-30 | $968.54M |
| 2025-06-30 | $975.96M |
| 2025-03-31 | $899.77M |
| 2024-12-31 | $896.97M |
| 2024-09-30 | $1.01B |
| 2024-06-30 | $973.93M |
| 2024-03-31 | $979.12M |
| 2023-12-31 | $929.42M |
| 2023-09-30 | $813.39M |
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.