MIGBX Performance — Massachusetts Investors Growth Stock Fund, Class B
Data updated: 2026-07-23
MIGBX returned −0.99% year to date and +9.13% over one year to May 2026. Annualised returns are +12.08% over 3 years and +7.06% over 5 years. The fund trailed its US Large Growth category average: $100 invested three years ago grew to $141, against $187 for the category, and to $109 over one year, against $125. Volatility over the past three years was 13.06% a year. In the 12 months to May 2026 the fund lost a net $2.5B, and assets reached $9.23B.
MIGBX Growth of $100
What $100 invested in Massachusetts Investors Growth Stock Fund grew to, compounded from monthly returns reported on SEC Form N-PORT, against the US Large Growth category average over the same months.
| Period | MIGBX | Category average |
|---|---|---|
| 1 year (Jun 2025 – May 2026) | $109 | $125 |
| 3 years (Jun 2023 – May 2026) | $141 | $187 |
| 5 years (Jun 2021 – May 2026) | $141 | $176 |
| Since data start (Sep 2019 – May 2026) | $206 | $274 |
MIGBX Trailing Returns
Total returns to May 2026, from SEC N-PORT.
| Period | Total return |
|---|---|
| YTD | −0.99% |
| 1 year | +9.13% |
| 3 years (annualised) | +12.08% |
| 5 years (annualised) | +7.06% |
MIGBX Annual Returns
Calendar-year total returns of Massachusetts Investors Growth Stock Fund, compounded from monthly SEC N-PORT returns. Partial years show the months covered.
| Year | Total return |
|---|---|
| 2026 (Jan–May) | −0.99% |
| 2025 | +9.05% |
| 2024 | +15.48% |
| 2023 | +23.14% |
| 2022 | −19.81% |
| 2021 | +25.24% |
| 2020 | +21.55% |
| 2019 (Sep–Dec) | +10.07% |
MIGBX 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 | −0.8% | −2.5% | −6.5% | +7.3% | +2.0% | — | — | — | — | — | — | — |
| 2025 | +2.4% | −1.4% | −6.2% | −1.4% | +6.0% | +3.8% | +2.7% | +0.6% | +1.7% | +2.2% | −1.1% | 0.0% |
| 2024 | +1.0% | +4.6% | +2.2% | −4.5% | +4.9% | +2.3% | +1.2% | +1.9% | +2.3% | −2.7% | +4.4% | −2.4% |
| 2023 | +6.1% | −3.7% | +5.3% | +1.2% | +0.1% | +6.6% | +1.5% | −1.3% | −5.4% | −1.9% | +10.3% | +3.4% |
| 2022 | −5.5% | −4.4% | +2.4% | −7.7% | 0.0% | −6.8% | +8.5% | −5.0% | −10.4% | +6.2% | +8.0% | −4.7% |
| 2021 | −2.4% | +2.6% | +3.1% | +6.7% | −0.5% | +2.2% | +4.5% | +2.2% | −5.6% | +6.7% | −2.0% | +6.1% |
| 2020 | +0.3% | −7.6% | −11.5% | +12.0% | +5.6% | +1.8% | +6.4% | +6.0% | −2.1% | −2.5% | +10.1% | +3.8% |
| 2019 | — | — | — | — | — | — | — | — | +0.9% | +0.7% | +4.7% | +3.4% |
MIGBX Risk
Risk measures from monthly returns over Jun 2023 – May 2026.
- 3-year volatility (annualised): 13.06%
- 3-year Sharpe ratio: 0.58 (vs 4.5% risk-free rate)
- Best month: +10.27% (Nov 2023)
- Worst month: −6.45% (Mar 2026)
MIGBX Fund Flows
Monthly money in and out of Massachusetts Investors Growth Stock Fund, from SEC Form N-PORT.
- 12-month net flow: −$2.5B
- 12-month gross sales (incl. reinvestments): $1.9B
- Sales ÷ redemptions: 0.44×
| Month | Sales | Redemptions | Net flow |
|---|---|---|---|
| May 2026 | $44.0M | $551.3M | −$507.3M |
| Apr 2026 | $95.5M | $227.2M | −$131.7M |
| Mar 2026 | $70.3M | $306.7M | −$236.4M |
| Feb 2026 | $67.6M | $230.1M | −$162.5M |
| Jan 2026 | $66.4M | $680.0M | −$613.6M |
| Dec 2025 | $1.1B | $397.7M | $696.1M |
| Nov 2025 | $57.5M | $600.1M | −$542.5M |
| Oct 2025 | $66.3M | $295.2M | −$228.9M |
| Sep 2025 | $56.4M | $322.0M | −$265.5M |
| Aug 2025 | $144.8M | $201.6M | −$56.9M |
| Jul 2025 | $108.9M | $326.5M | −$217.6M |
| Jun 2025 | $65.2M | $293.7M | −$228.5M |
MIGBX Assets Under Management
Net assets of Massachusetts Investors Growth Stock Fund by report date, from SEC N-PORT filings.
| Report date | Net assets |
|---|---|
| 2026-05-31 | $9.23B |
| 2026-02-28 | $9.87B |
| 2025-11-30 | $11.33B |
| 2025-08-31 | $12.01B |
| 2025-05-31 | $11.75B |
| 2025-02-28 | $12.46B |
| 2024-11-30 | $13.09B |
| 2024-08-31 | $12.94B |
| 2024-05-31 | $12.57B |
| 2024-02-29 | $12.51B |
| 2023-11-30 | $11.73B |
| 2023-08-31 | $11.48B |
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.