A.I.M. Mutual and the Massachusetts Assigned Risk Pool sit on opposite sides of the same market. A.I.M. Mutual is a private carrier in the voluntary market, competing to write the workers comp business it wants. The Assigned Risk Pool is the residual market, the state-connected backstop that covers employers the voluntary market declines. If a carrier like A.I.M. Mutual is willing to write you, that is almost always the better home; the pool is where you go when no one else will take you.
Who this is for: Massachusetts owners weighing a voluntary carrier against the pool, or trying to move out of the pool once they are insurable again.
The short version
- A.I.M. Mutual is the open market. A Massachusetts-based mutual that specializes in workers comp and competes on price and service.
- The pool is the last resort. A residual market run through WCRIBMA for businesses the voluntary market declines.
- Price favors the open market. Pool rates are standardized, with no dividends and possible surcharges.
- You cannot just pick the pool. You generally must be declined by carriers first.
- The pool is temporary. The goal is to earn your way back to a carrier like A.I.M. Mutual.
Who each one is
Associated Industries of Massachusetts Mutual Insurance Company, known as A.I.M. Mutual, is a Massachusetts-domiciled mutual insurer focused on workers comp. Being a mutual, it is owned by its policyholders and can return value through dividends when results allow. It is one of several established voluntary carriers here, alongside insurers such as MEMIC and The Hartford. The Assigned Risk Pool, by contrast, is not a carrier you shop; it is the state's insurer of last resort, administered by WCRIBMA, that issues coverage through assigned servicing carriers.
Feature by feature
| Feature | A.I.M. Mutual (voluntary market) | Assigned Risk Pool (last resort) |
|---|---|---|
| Market type | Private, competitive carrier | State-connected residual market |
| Who can get it | Businesses the carrier chooses to write | Businesses the voluntary market declined |
| Pricing | Competitive, risk-based, room to shop | Standardized, with possible surcharges |
| Dividends | Possible for a mutual, subject to terms | None |
| Safety and loss-control services | Commonly offered | Limited; built to provide coverage, not service |
| Best fit | Most insurable Massachusetts employers | Hard-to-place risks with no other option |
When the pool is the right call
The pool earns its place when the voluntary market genuinely will not write you: a severe claims history, a class code carriers avoid, or a lapse that makes underwriters nervous. In those cases the pool keeps you compliant and operating, which beats going uninsured by a wide margin. What you should not do is default to the pool without shopping, because a carrier like A.I.M. Mutual may well write the same risk at a better price. See what to do when you cannot find coverage.
Moving from the pool to a voluntary carrier
If you are in the pool today, treat it as temporary. Tighten safety, keep claims down, and lower your experience mod, then have an agent re-market you at renewal. As your profile improves, voluntary carriers become willing again, and the move off the pool usually brings a lower premium and better service. Our guide to reducing workers comp costs covers the levers that get you there.
A quick Massachusetts example
Illustrative, not a quote. A framing contractor in Fall River lands in the assigned risk pool after a bad claim year. Coverage stays in force, but the premium is high and there is little flexibility. The owner runs a simple safety program, the claim ages off, and the experience mod falls. At renewal, an agent markets the account to voluntary carriers, and A.I.M. Mutual writes it at a lower rate with loss-control support the pool never offered. Same business, better home, once it was insurable again. Trade detail is on our workers comp for contractors page.
Real questions Massachusetts owners ask
What is the difference between A.I.M. Mutual and the Massachusetts Assigned Risk Pool?
A.I.M. Mutual is a private carrier in the voluntary market that competes to write workers comp it wants. The Assigned Risk Pool is the residual market, a state-connected backstop that covers businesses the voluntary market declines. One is a competitive home; the other is a last resort.
Is A.I.M. Mutual cheaper than the assigned risk pool?
Voluntary-market carriers are generally priced more competitively than the pool, because the pool uses standardized rates with no dividends and possible surcharges. We do not promise a specific number, but for a business a carrier is willing to write, the open market usually wins on price and flexibility.
Who is A.I.M. Mutual?
Associated Industries of Massachusetts Mutual Insurance Company (A.I.M. Mutual) is a Massachusetts-based mutual insurer that specializes in workers comp. As a mutual, it is owned by its policyholders and can return value through dividends when results allow, subject to its own terms.
Can I just choose the pool if I want guaranteed coverage?
Not as a first choice. The pool is designed for businesses the voluntary market declines, and you generally have to show you were turned down before it applies. If a carrier like A.I.M. Mutual will write you, that is almost always the better placement.
If I'm in the pool now, how do I move to a carrier like A.I.M. Mutual?
Clean up your claims history, run a safety and return-to-work program to lower your experience mod, and have an agent re-market you to the voluntary market at renewal. As your risk profile improves, private carriers become willing to write you again.
Are there other voluntary carriers besides A.I.M. Mutual?
Yes. Massachusetts has an active voluntary market, including insurers like MEMIC and The Hartford among many others. An independent agent shops several at once, which is the point of using a broker instead of applying to one carrier at a time.
Does A.I.M. Mutual offer anything the pool does not?
Typically yes. Voluntary carriers compete on more than price, offering loss-control and safety services, claims handling, and pricing flexibility. The pool provides the coverage you need to stay compliant, but it is built as a backstop, not a service relationship.
Why Massachusetts owners choose Morrow
- We shop the whole Massachusetts market for you. Massachusetts has no state-run insurer, so coverage comes from private carriers, or, if no carrier will take you, from the state's backup option (officially the Massachusetts Workers' Compensation Assigned Risk Pool, run through WCRIBMA, the licensed bureau that administers that pool). We check both so you are not stuck with the first price you are handed.
- We catch pricing mistakes. Your price depends heavily on the category your work falls into for pricing (the class code). Put people in the wrong category and you overpay for years. We review your payroll and classifications before you buy.
- Proof of coverage, fast. Need a certificate (proof of coverage) for a general contractor or a landlord before Monday? We turn those around the same business day for most carriers.
- We help lower the score that drives your price. Insurers give you a score based on your past claims that raises or lowers your cost (the experience modification rate). We review it each year, flag errors, and connect you with return-to-work and safety resources that bring it down.
- Real people when a claim happens. When someone gets hurt, we stay involved through the life of the claim, not just at renewal.
Related Massachusetts guides
Every Massachusetts business is set up a little differently. These companion guides answer the same question for other situations, plus the national explainers behind the terms used here.
- Business insurance in Massachusetts (start here)
- Massachusetts workers comp: the owner's overview
- I own an LLC: do I need workers comp?
- I'm a sole proprietor: do I need workers comp?
- I own a corporation (C-corp or S-corp): do I need it?
- We're a partnership: do we need workers comp?
- We're a nonprofit: do we need workers comp?
- My workers are 1099: do I still need it?
- Only part-time or seasonal staff: do I need it?
- I only employ family: do I need workers comp?
- Remote or out-of-state staff: do I need MA coverage?
- What happens if I don't carry workers comp?
- How much does workers comp cost in Massachusetts?
- How do I get workers comp (even if turned down)?
- What insurance do I need for a contractor license?
- Does Massachusetts have a state workers comp fund?
- The Massachusetts Assigned Risk Pool, explained
- Can't find workers comp anywhere in Massachusetts?
- Workers compensation insurance, explained
- What workers comp costs (national guide)
- What is an experience mod, and how do I lower it?
- Workers comp vs employers liability
- Workers comp for contractors
This guide is general information, not legal advice. Massachusetts rules and penalty amounts can change, so verify current requirements with the Massachusetts Department of Industrial Accidents or a licensed advisor before you rely on them. Last updated: July 2026.