Mass. Gen. Laws ch. 161A § 32
The arbitrator shall be limited in making his award to choosing between the last best offers of the parties on each issue as certified in the mediator's report or any award in the range between the last best offers of the parties. The arbitrator shall make no award on any issue found by him to be not authorized by law to be submitted to arbitration, but shall state such finding in his written opinion. Within 30 calendar days of an award, the arbitrator shall issue a written opinion inclusive of an analysis of all statutory factors applicable to the proceedings. Any determination by the arbitrator, if supported by material and substantial evidence on the record, shall be binding upon the parties and upon the appropriate legislative or appropriating body and may be enforced at the insistence of either party or by the arbitrator in the superior court. The scope of arbitration shall be limited to wages, hours, and conditions of employment and shall not include any provisions for any cost of living adjustment which are based on changes in the consumer price index after the expiration of the contract period covered by the award. In addition, any wage or salary adjustments shall be expressed in percent or dollar amounts, and in no case shall there be any provision for salary adjustments to occur after the expiration of the contract period covered by the award.
The cost, if any, of the mediation and of arbitration proceedings exclusive of the expenses of the individual parties provided for under sections 28 to 32, inclusive, shall be divided equally by the parties and shall be in accordance with a schedule of payments established by the American Arbitration Association.
Mass. Gen. Laws ch. 161A, § 32