During the period in office of the governments led by Joseph Wirth in 1921/22 and in which the SPD participated, Müller demanded as parliamentary leader of the SPD that budget consolidation would involve first and foremost the higher taxation of wealth rather than of consumption. This led to confrontations with the "bourgeois" parties. Similarly, the reunification of SPD and USPD resulted in a move to the left of the new SPD. Arguments between SPD and DVP about economic issues like the eight-hour work day introduced in late 1918 (but opposed by the DVP) finally caused the coalition's end in November 1922.