OTCBX Performance — MFS Mid Cap Growth Fund, Class B
Data updated: 2026-07-23
OTCBX returned +3.50% year to date and +3.81% over one year to May 2026. Annualised returns are +11.11% over 3 years and +2.88% over 5 years. The fund trailed its US Mid-Cap Growth category average: $100 invested three years ago grew to $137, against $157 for the category, and to $104 over one year, against $119. Volatility over the past three years was 16.22% a year. In the 12 months to May 2026 the fund took in a net $68.2M, and assets reached $13.78B.
OTCBX Growth of $100
What $100 invested in MFS 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 | OTCBX | Category average |
|---|---|---|
| 1 year (Jun 2025 – May 2026) | $104 | $119 |
| 3 years (Jun 2023 – May 2026) | $137 | $157 |
| 5 years (Jun 2021 – May 2026) | $115 | $129 |
| Since data start (Sep 2019 – May 2026) | $163 | $197 |
OTCBX Trailing Returns
Total returns to May 2026, from SEC N-PORT.
| Period | Total return |
|---|---|
| YTD | +3.50% |
| 1 year | +3.81% |
| 3 years (annualised) | +11.11% |
| 5 years (annualised) | +2.88% |
OTCBX Annual Returns
Calendar-year total returns of MFS Mid Cap Growth Fund, compounded from monthly SEC N-PORT returns. Partial years show the months covered.
| Year | Total return |
|---|---|
| 2026 (Jan–May) | +3.50% |
| 2025 | +2.63% |
| 2024 | +13.55% |
| 2023 | +20.14% |
| 2022 | −29.07% |
| 2021 | +12.90% |
| 2020 | +34.34% |
| 2019 (Sep–Dec) | +4.76% |
OTCBX 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 | −0.7% | +0.6% | −6.4% | +8.4% | +2.2% | — | — | — | — | — | — | — |
| 2025 | +5.9% | −5.2% | −6.6% | +2.3% | +6.7% | +5.5% | −0.3% | +0.4% | +0.4% | −2.0% | −1.7% | −1.8% |
| 2024 | +1.0% | +7.5% | +1.7% | −6.2% | +2.5% | +0.9% | +1.2% | +1.2% | +2.1% | −2.0% | +9.9% | −6.0% |
| 2023 | +7.1% | −2.6% | +2.8% | −1.0% | −0.5% | +6.5% | +1.5% | −1.3% | −5.5% | −3.4% | +11.0% | +5.1% |
| 2022 | −14.2% | −3.0% | +1.2% | −10.3% | −1.6% | −6.6% | +10.8% | −5.6% | −8.6% | +5.5% | +7.0% | −5.3% |
| 2021 | −2.5% | +0.4% | −0.6% | +5.8% | −2.3% | +4.1% | +3.9% | +3.2% | −4.8% | +6.5% | −3.8% | +3.0% |
| 2020 | +2.9% | −6.3% | −13.2% | +12.5% | +10.1% | +1.5% | +7.5% | +3.1% | +0.3% | −1.7% | +9.8% | +6.3% |
| 2019 | — | — | — | — | — | — | — | — | −1.3% | +0.4% | +4.5% | +1.1% |
OTCBX Risk
Risk measures from monthly returns over Jun 2023 – May 2026.
- 3-year volatility (annualised): 16.22%
- 3-year Sharpe ratio: 0.41 (vs 4.5% risk-free rate)
- Best month: +11.04% (Nov 2023)
- Worst month: −6.57% (Mar 2025)
OTCBX Fund Flows
Monthly money in and out of MFS Mid Cap Growth Fund, from SEC Form N-PORT.
- 12-month net flow: $68.2M
- 12-month gross sales (incl. reinvestments): $4.8B
- Sales ÷ redemptions: 1.01×
| Month | Sales | Redemptions | Net flow |
|---|---|---|---|
| May 2026 | $156.4M | $317.8M | −$161.5M |
| Apr 2026 | $138.8M | $287.0M | −$148.2M |
| Mar 2026 | $254.4M | $464.1M | −$209.7M |
| Feb 2026 | $177.1M | $351.9M | −$174.8M |
| Jan 2026 | $231.1M | $405.0M | −$173.9M |
| Dec 2025 | $2.1B | $447.2M | $1.7B |
| Nov 2025 | $253.4M | $373.4M | −$120.0M |
| Oct 2025 | $294.4M | $377.6M | −$83.3M |
| Sep 2025 | $361.4M | $296.0M | $65.4M |
| Aug 2025 | $260.8M | $250.8M | $10.0M |
| Jul 2025 | $411.7M | $864.4M | −$452.7M |
| Jun 2025 | $143.8M | $324.9M | −$181.2M |
OTCBX Assets Under Management
Net assets of MFS Mid Cap Growth Fund by report date, from SEC N-PORT filings.
| Report date | Net assets |
|---|---|
| 2026-05-31 | $13.78B |
| 2026-02-28 | $13.79B |
| 2025-11-30 | $14.58B |
| 2025-08-31 | $15.19B |
| 2025-05-31 | $14.95B |
| 2025-02-28 | $14.94B |
| 2024-11-30 | $16.07B |
| 2024-08-31 | $14.72B |
| 2024-05-31 | $14.09B |
| 2024-02-29 | $14.65B |
| 2023-11-30 | $13.03B |
| 2023-08-31 | $13.08B |
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.