STMGX Performance — American Beacon Stephens Mid-Cap Growth Fund, Investor Class
Data updated: 2026-08-11
STMGX returned +13.65% year to date and +16.80% over one year to Jun 2026. Annualised returns are +15.96% over 3 years and +6.42% over 5 years. Against its US Mid-Cap Growth category average the fund came out ahead over three years but behind over one: $100 invested three years ago grew to $156, against $152 for the category, and to $117 over one year, against $118. Volatility over the past three years was 15.78% a year. In the 12 months to Jun 2026 the fund took in a net $150.8M, and assets reached $772.34M.
STMGX Growth of $100
What $100 invested in American Beacon Stephens Mid-Cap Growth Fund grew to, compounded from monthly returns reported on SEC Form N-PORT, against the US Mid-Cap Growth category average over the same months.
| Period | STMGX | Category average |
|---|---|---|
| 1 year (Jul 2025 – Jun 2026) | $117 | $118 |
| 3 years (Jul 2023 – Jun 2026) | $156 | $152 |
| 5 years (Jul 2021 – Jun 2026) | $137 | $129 |
| Since data start (Jul 2019 – Jun 2026) | $212 | $203 |
STMGX Trailing Returns
Total returns to Jun 2026, from SEC N-PORT.
| Period | Total return |
|---|---|
| YTD | +13.65% |
| 1 year | +16.80% |
| 3 years (annualised) | +15.96% |
| 5 years (annualised) | +6.42% |
STMGX Annual Returns
Calendar-year total returns of American Beacon Stephens Mid-Cap Growth Fund, compounded from monthly SEC N-PORT returns. Partial years show the months covered.
| Year | Total return |
|---|---|
| 2026 (Jan–Jun) | +13.65% |
| 2025 | +12.58% |
| 2024 | +13.07% |
| 2023 | +25.23% |
| 2022 | −28.26% |
| 2021 | +12.18% |
| 2020 | +39.80% |
| 2019 (Jul–Dec) | +4.08% |
STMGX 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 | +0.6% | +1.8% | −5.8% | +6.7% | +6.3% | +3.8% | — | — | — | — | — | — |
| 2025 | +4.6% | −4.8% | −6.2% | +1.7% | +7.7% | +7.1% | +1.7% | +0.8% | +1.8% | +0.3% | −0.8% | −0.9% |
| 2024 | −0.5% | +7.1% | +2.2% | −6.0% | +2.1% | +0.2% | +0.1% | +2.2% | +1.6% | −0.9% | +11.2% | −5.7% |
| 2023 | +8.7% | −2.5% | +4.2% | −1.9% | +0.4% | +6.9% | +2.5% | −2.9% | −4.5% | −3.1% | +10.1% | +6.3% |
| 2022 | −12.2% | −1.2% | +0.8% | −10.5% | −3.8% | −8.1% | +11.9% | −5.1% | −9.0% | +8.2% | +5.0% | −5.4% |
| 2021 | −2.0% | +2.6% | −1.6% | +5.2% | −1.5% | +4.2% | +3.3% | +0.7% | −4.0% | +6.8% | −4.5% | +3.0% |
| 2020 | +0.7% | −6.2% | −13.5% | +16.1% | +11.8% | +3.3% | +7.1% | +2.6% | −3.3% | −1.5% | +13.5% | +7.3% |
| 2019 | — | — | — | — | — | — | +0.6% | −3.2% | −1.1% | +1.0% | +5.9% | +1.0% |
STMGX Risk
Risk measures from monthly returns over Jul 2023 – Jun 2026.
- 3-year volatility (annualised): 15.78%
- 3-year Sharpe ratio: 0.73 (vs 4.5% risk-free rate)
- Best month: +11.20% (Nov 2024)
- Worst month: −6.25% (Mar 2025)
STMGX Fund Flows
Monthly money in and out of American Beacon Stephens Mid-Cap Growth Fund, from SEC Form N-PORT.
- 12-month net flow: $150.8M
- 12-month gross sales (incl. reinvestments): $377.5M
- Sales ÷ redemptions: 1.67×
| Month | Sales | Redemptions | Net flow |
|---|---|---|---|
| Jun 2026 | $66.7M | $12.8M | $54.0M |
| May 2026 | $18.6M | $13.3M | $5.4M |
| Apr 2026 | $14.0M | $14.0M | $47K |
| Mar 2026 | $16.0M | $49.5M | −$33.6M |
| Feb 2026 | $7.9M | $14.6M | −$6.7M |
| Jan 2026 | $12.5M | $17.1M | −$4.6M |
| Dec 2025 | $116.9M | $30.2M | $86.7M |
| Nov 2025 | $5.3M | $13.7M | −$8.4M |
| Oct 2025 | $78.7M | $14.5M | $64.1M |
| Sep 2025 | $4.4M | $10.1M | −$5.7M |
| Aug 2025 | $28.6M | $15.8M | $12.8M |
| Jul 2025 | $7.9M | $21.1M | −$13.2M |
STMGX Assets Under Management
Net assets of American Beacon Stephens Mid-Cap Growth Fund by report date, from SEC N-PORT filings.
| Report date | Net assets |
|---|---|
| 2026-06-30 | $772.34M |
| 2026-03-31 | $603.35M |
| 2025-12-31 | $670.11M |
| 2025-09-30 | $687.40M |
| 2025-06-30 | $664.96M |
| 2025-03-31 | $849.61M |
| 2024-12-31 | $800.02M |
| 2024-09-30 | $773.57M |
| 2024-06-30 | $751.52M |
| 2024-03-31 | $758.14M |
| 2023-12-31 | $679.32M |
| 2023-09-30 | $586.56M |
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.