  Public procurement refers to the purchase by public sector entities, such as
government departments or local authorities, of Services, Goods, or Works. It
accounts for a significant share of OECD countries' expenditures. However,
while governments are expected to execute them as efficiently as possible,
there is a lack of methodologies for an adequate comparison of procurement
activity between institutions at different scales, which represents a challenge
for policymakers and academics. Here, we propose using methods from urban
scaling laws literature to study public procurement activity among 278
Portuguese municipalities between 2011 and 2018. We find that public
procurement expenditure scales sub-linearly with population size, indicating an
economy of scale for public spending as cities increase their population size.
Moreover, when looking at the municipal Scale-Adjusted Indicators (the
deviations from the scaling laws) by contract type -- Works, Goods, and
Services -- we obtain a new local characterization of municipalities based on
the similarity of procurement activity. These results make up a framework for
quantitatively studying local public expenditure by enabling policymakers a
more appropriate ground for comparative analysis.
