MCBKX Performance — MFS Core Bond Fund, Class R4
Data updated: 2026-09-28
MCBKX returned −0.52% year to date and +2.73% over one year to Jul 2026. The annualised 3-year return is +3.94%. The fund trailed its Intermediate Core Bond category average: $100 invested three years ago grew to $112, against $113 for the category, and to $103 over one year, against $103. Volatility over the past three years was 5.62% a year. In the 12 months to Jul 2026 the fund took in a net $2.7M, and assets reached $34.42M.
MCBKX Growth of $100
What $100 invested in MFS Core Bond Fund grew to, compounded from monthly returns reported on SEC Form N-PORT, against the Intermediate Core Bond category average over the same months.
| Period | MCBKX | Category average |
|---|---|---|
| 1 year (Aug 2025 – Jul 2026) | $103 | $103 |
| 3 years (Aug 2023 – Jul 2026) | $112 | $113 |
| Since data start (May 2022 – Jul 2026) | $113 | $111 |
MCBKX Trailing Returns
Total returns to Jul 2026, from SEC N-PORT.
| Period | Total return |
|---|---|
| YTD | −0.52% |
| 1 year | +2.73% |
| 3 years (annualised) | +3.94% |
MCBKX Annual Returns
Calendar-year total returns of MFS Core Bond Fund, compounded from monthly SEC N-PORT returns. Partial years show the months covered.
| Year | Total return |
|---|---|
| 2026 (Jan–Jul) | −0.52% |
| 2025 | +7.19% |
| 2024 | +1.77% |
| 2023 | +6.44% |
| 2022 (May–Dec) | −1.95% |
MCBKX 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 | +0.2% | +1.6% | −1.8% | +0.1% | +0.3% | +0.4% | −1.3% | — | — | — | — | — |
| 2025 | +0.6% | +2.2% | 0.0% | +0.3% | −0.7% | +1.5% | −0.1% | +1.1% | +1.1% | +0.7% | +0.5% | −0.2% |
| 2024 | 0.0% | −1.4% | +0.9% | −2.4% | +1.8% | +1.0% | +2.3% | +1.4% | +1.3% | −2.3% | +1.1% | −1.7% |
| 2023 | +3.5% | −2.5% | +2.4% | +0.5% | −1.1% | −0.2% | +0.2% | −0.7% | −2.5% | −1.7% | +4.6% | +3.9% |
| 2022 | — | — | — | — | 0.0% | +1.1% | +2.3% | −2.7% | −4.3% | −1.2% | +3.8% | −0.6% |
MCBKX Risk
Risk measures from monthly returns over Aug 2023 – Jul 2026.
- 3-year volatility (annualised): 5.62%
- 3-year Sharpe ratio: -0.10 (vs 4.5% risk-free rate)
- Best month: +4.57% (Nov 2023)
- Worst month: −2.55% (Sep 2023)
MCBKX Fund Flows
Monthly money in and out of MFS Core Bond Fund, from SEC Form N-PORT.
- 12-month net flow: $2.7M
- 12-month gross sales (incl. reinvestments): $4.2M
- Sales ÷ redemptions: 2.83×
| Month | Sales | Redemptions | Net flow |
|---|---|---|---|
| Jul 2026 | $569K | $194K | $375K |
| Jun 2026 | $239K | $72K | $167K |
| May 2026 | $776K | $67K | $709K |
| Apr 2026 | $320K | $200K | $120K |
| Mar 2026 | $166K | $56K | $110K |
| Feb 2026 | $261K | $157K | $104K |
| Jan 2026 | $251K | $394K | −$143K |
| Dec 2025 | $268K | $76K | $192K |
| Nov 2025 | $313K | $56K | $258K |
| Oct 2025 | $520K | $128K | $393K |
| Sep 2025 | $316K | $7K | $308K |
| Aug 2025 | $237K | $89K | $148K |
MCBKX Assets Under Management
Net assets of MFS Core Bond Fund by report date, from SEC N-PORT filings.
| Report date | Net assets |
|---|---|
| 2026-07-31 | $34.42M |
| 2026-04-30 | $33.80M |
| 2026-01-31 | $33.86M |
| 2025-10-31 | $33.71M |
| 2025-07-31 | $32.36M |
| 2025-04-30 | $31.97M |
| 2025-01-31 | $30.85M |
| 2024-10-31 | $30.67M |
| 2024-07-31 | $30.35M |
| 2024-04-30 | $29.09M |
| 2024-01-31 | $29.60M |
| 2023-10-31 | $26.61M |
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.