BIGIX Performance — William Blair International Growth Fund, Class I
Data updated: 2026-08-14
BIGIX returned +16.78% year to date and +21.89% over one year to Jun 2026. Annualised returns are +13.52% over 3 years and +3.24% 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 15.38% a year. In the 12 months to Jun 2026 the fund lost a net $234.6M, and assets reached $1.16B.
BIGIX Growth of $100
What $100 invested in William Blair 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 | BIGIX | 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) | $184 | $178 |
BIGIX Trailing Returns
Total returns to Jun 2026, from SEC N-PORT.
| Period | Total return |
|---|---|
| YTD | +16.78% |
| 1 year | +21.89% |
| 3 years (annualised) | +13.52% |
| 5 years (annualised) | +3.24% |
BIGIX Annual Returns
Calendar-year total returns of William Blair International Growth Fund, compounded from monthly SEC N-PORT returns. Partial years show the months covered.
| Year | Total return |
|---|---|
| 2026 (Jan–Jun) | +16.78% |
| 2025 | +18.01% |
| 2024 | +2.38% |
| 2023 | +15.38% |
| 2022 | −28.33% |
| 2021 | +9.01% |
| 2020 | +31.98% |
| 2019 (Jul–Dec) | +9.39% |
BIGIX 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% | +4.8% | −10.3% | +9.6% | +6.1% | +1.1% | — | — | — | — | — | — |
| 2025 | +3.4% | −0.6% | −2.7% | +4.0% | +5.4% | +3.1% | −2.1% | +1.4% | +3.2% | +1.7% | −2.2% | +2.5% |
| 2024 | −0.7% | +4.7% | +2.5% | −5.5% | +3.7% | +0.2% | +1.8% | +2.5% | +0.3% | −4.3% | +0.1% | −2.2% |
| 2023 | +7.8% | −2.9% | +3.6% | +0.9% | −1.6% | +3.3% | +0.9% | −4.6% | −5.4% | −3.9% | +11.3% | +6.4% |
| 2022 | −11.4% | −4.4% | −0.5% | −9.3% | −1.2% | −8.1% | +8.9% | −6.1% | −10.2% | +6.6% | +10.3% | −4.2% |
| 2021 | +0.1% | 0.0% | −1.4% | +6.3% | +2.4% | +0.9% | +1.7% | +3.6% | −5.7% | +3.9% | −4.0% | +1.5% |
| 2020 | −0.8% | −6.1% | −14.0% | +9.3% | +8.6% | +5.5% | +7.4% | +6.2% | −0.9% | −1.3% | +10.6% | +6.5% |
| 2019 | — | — | — | — | — | — | −1.3% | −0.8% | +0.9% | +3.9% | +2.5% | +4.0% |
BIGIX Risk
Risk measures from monthly returns over Jul 2023 – Jun 2026.
- 3-year volatility (annualised): 15.38%
- 3-year Sharpe ratio: 0.59 (vs 4.5% risk-free rate)
- Best month: +11.28% (Nov 2023)
- Worst month: −10.35% (Mar 2026)
BIGIX Fund Flows
Monthly money in and out of William Blair International Growth Fund, from SEC Form N-PORT.
- 12-month net flow: −$234.6M
- 12-month gross sales (incl. reinvestments): $269.7M
- Sales ÷ redemptions: 0.53×
| Month | Sales | Redemptions | Net flow |
|---|---|---|---|
| Jun 2026 | $6.3M | $13.7M | −$7.4M |
| May 2026 | $6.5M | $13.3M | −$6.8M |
| Apr 2026 | $5.9M | $17.9M | −$12.0M |
| Mar 2026 | $6.7M | $32.1M | −$25.4M |
| Feb 2026 | $5.8M | $21.8M | −$16.0M |
| Jan 2026 | $5.8M | $75.1M | −$69.2M |
| Dec 2025 | $202.8M | $113.0M | $89.9M |
| Nov 2025 | $5.7M | $39.9M | −$34.3M |
| Oct 2025 | $4.6M | $35.5M | −$30.9M |
| Sep 2025 | $5.8M | $49.0M | −$43.2M |
| Aug 2025 | $6.5M | $56.3M | −$49.7M |
| Jul 2025 | $7.4M | $37.0M | −$29.5M |
BIGIX Assets Under Management
Net assets of William Blair International Growth Fund by report date, from SEC N-PORT filings.
| Report date | Net assets |
|---|---|
| 2026-06-30 | $1.16B |
| 2026-03-31 | $1.01B |
| 2025-12-31 | $1.12B |
| 2025-09-30 | $1.27B |
| 2025-06-30 | $1.36B |
| 2025-03-31 | $1.33B |
| 2024-12-31 | $1.36B |
| 2024-09-30 | $1.54B |
| 2024-06-30 | $1.48B |
| 2024-03-31 | $1.51B |
| 2023-12-31 | $1.43B |
| 2023-09-30 | $1.38B |
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.