In the public sphere, a management by measurement (MBM) movement can be traced. Practitioners attempt to strengthen the transparency and effectiveness of administrative systems by introducing rational measurement cycles. When issues are managed, ambitions must be stated, options must be assessed, optimal options must be chosen and performance must be monitored and evaluated. This cycle rests upon assumptions that are often untenable. When issues are ambiguous, interpretative spaces exist; when interpretative spaces exist, strict measurement cycles do not work because required conditions and assumptions cannot be met. This article explores the nature of interpretative spaces by identifying three types of public management practice. In this typology of public management, practices differ in terms of the extent to which issues can be classified, as well as the extent to which standards are contested. Management by measurement fits canonical practices where issues are known and standards are shared, it is argued, but is less appropriate for evaluating non-canonical practices and practices-in-transition where such a classification of issues is weak and consensus on standard is absent. MBM focuses on data; the other practices require dialogue in order to manage ambiguity and interpretative spaces.