Corruption is ostensibly difficult to measure, especially when it is unclear which form of corruption is captured, which part of the corrupt deal is visible in the data, and how different proxies relate to each other. Due to the emergence of innovations in measuring corruption in public procurement, this paper can provide a comprehensive review of quantitative corruption proxies, conceptualise how different indicators capture different aspects of corruption, and identify gaps in the measurement landscape. Institutionalised, wellestablished corruption in government contracting aims to bypass fair and open competition in order to allocate contracts to companies belonging to the corrupt group. This requires at least
- corrupt transactions allowing for rent generation,
- particularistic relations underpinning collective action of corrupt groups;
- organisations enabling rent allocation (public organisations); and
- organisations extracting corrupt rents (private companies)
These four requirements of corrupt contracting serve as a framework for the review. We find that there is a surprisingly wide array of indicators validated in particular contexts, leaving generalisability unclear. It is also suggested that the academic literature has largely been preoccupied with one or the other type of corruption proxies such as personal connections without recognising their complementarities. Given the clandestine and often complex character of corrupt deals, a comprehensive measurement approach is advocated where each indicator sheds light on different aspects of the same corrupt phenomena.