This research aim to analyze the sources of changes in sectoral output in Indonesia in the periods from 1975-1985, 1985-1995, and 1995-2003, as well as to understand and measure the contribution of end demand, technology and synergy to total change in economic output in these periods. The decomposition output approach was used to measure the effect of end demand, technology and synergy. The research used the 66 sector total transaction input-output table from 1975 to 2003. The research found that end demand dominated the change in output during these periods, while technology played a relatively small role. Despite this, the role of end demand in period III (1995-2003) fell to 59.73% from 87.64% in period I (1973-1985).