Proposition 2½ (Mass. Gen. L. c. 59, § 21C) is a Massachusetts statute that limits property tax assessments and, secondarily, automobile excise tax levies by Massachusetts municipalities. The name of the initiative refers to the 2.5% ceiling on total property taxes annually as well as the 2.5% limit on property tax increases. It was passed by ballot measure, specifically called an initiative petition within Massachusetts state law for any form of referendum voting, in 1980 and went into effect in 1982. The effort to enact the proposition was led by the anti-tax group Citizens for Limited Taxation. It is similar to other "tax revolt" measures passed around the same time in other parts of the United States. This particular proposition followed the movements of states such as California.