Mass. Gen. Laws ch. 32 § 77B
In any city or town which accepts the provisions of this section, as hereinafter provided, any laborer retired under section seventy-seven shall receive an annual pension equal to one half of his annual rate of regular compensation for full-time service as a laborer at his retirement, and if he has completed more than twenty years of service an additional amount equal to one per cent for each year of service after the first twenty; provided, that the total amount of such pension shall in no case exceed sixty-five per cent of said compensation.
This section shall take effect in a city or town having a plan D or plan E charter by the affirmative vote of two thirds of all the members of the city council, and in the case of any other city by vote of the city council subject to the provisions of its charter, and in a town by a majority vote at an annual town meeting.
Mass. Gen. Laws ch. 32, § 77B