Administrative reorganization has become widespread practice in modern democracies. Various case studies highlight the relevance of political ideology for bureaucratic contraction, others the role of socioeconomic pressure and institutional constraints. We examine these explanations in a study of the German Länder, which have substantially contracted their bureaucracies since the 1990s. Quantitative analysis of a novel data set of 479 ministerial departments in 13 Länder over two decades suggests that the ideological complexion of governments is a stronger predictor of administrative reform than socioeconomic pressure or institutional constraints. Moreover, interaction models show how socioeconomic and institutional variables condition the effect of ideology.