| Massachusetts Medical Society |
  |
47% |
| ProMutual |
  |
21% |
| CRICO (Risk Management Foundation) |
  |
21% |
| Lifespan |
  |
2% |
| Tufts/New England Medical Center |
  |
2% |
| Baystate Health Systems |
  |
1% |
| Lahey |
  |
1% |
| Caritas Christi |
  |
1% |
| Healthcare Underwriters Mutual |
  |
1% |
| Other* |
  |
5% |