"The senior homestead property tax exemption became available beginning in property tax year 2002, following voter approval of Referendum A in the 2000 General Election. The number of seniors claiming the exemption has grown over time, from 123,326 qualifying seniors...

This document from November 2016 is a history of the senior property tax exemption. The document was prepared by the Colorado Legislative Council Staff. History of the Senior Property Tax Exemption as of November 2016 - CLICK HERE