Recent advisory reports on the Dutch parliamentary system, public scrutiny, and parliamentary upheaval following transgressive behaviour by the old speaker of parliament have drawn attention to the...Show moreRecent advisory reports on the Dutch parliamentary system, public scrutiny, and parliamentary upheaval following transgressive behaviour by the old speaker of parliament have drawn attention to the functioning of parliamentary administrations. The support staff of parliaments is a scarcely covered topic in political science. In a new body of literature, this article is only the second to examine parliamentary staff size quantitatively. It fundamentally extends the scope of previous research from western democracies to a much broader population of parliaments. Drawing on both a functionalist and an institutionalist framework, it hypothesises that population size, population non-linearity, clientelism, parliamentary competition, an interaction between clientelism and parliamentary competition, parliamentary culture, and institutional isomorphism influence the number of institutional and committee staff in parliaments. This research uses house-level data from 161 countries over ten years and employs multilevel analysis to test these hypotheses. It finds strong support that population size, population size non-linearity, and institutional isomorphism influence staff size, while it finds mixed support for parliamentary competition as a predictor of staff size. There was no support for parliamentary culture, clientelism, and the clientelism-competition interaction hypotheses. Additionally, previously thought insignificant predictors of staff size, such as assembly size and parliamentary powers, were, in fact, significant. This article is the first to look at parliamentary administrations, which are vital to the functioning of primary democratic institutions, from a global perspective. Due to the mixed results, it calls for more extensive research on different types of staff, further disentangling of the mechanisms posited, and further data collection to progress understanding of this veiled political and administrative institution.Show less