In light of the growing public spending in many regions of the world, this study scrutinizes relevant determinants of core public administration expenditure at the cantonal level in Switzerland, focusing particularly on New Public Management (NPM) reforms. The empirical study comprises all 26 cantons in the period from 1993 through 2014 and uses both cross‐sectional and longitudinal analytical methods. In addition to NPM, we control for various variables related to political parties, institutions, socioeconomics and culture. The results show no clear relationship between NPM reforms and expenditure, although such reforms were often intended to cut costs. Our explanation for this finding is that NPM as a concept is rather inconsistent. Various control variables are either positively or negatively related with expenditure. All in all, our findings suggest that public expenditure is still mostly determined by politics and can only be influenced by administrative reforms within certain narrow limits.