This is an Accepted Manuscript of an article published by Inderscience in International Journal of Procurement Management (IJPM, Vol. 13, No. 2, 2020) on 9 April 2020, available online: https://doi.org/10.1504/ijpm.2020.10021016 1 Efficiency and Bid Rigging in Simultaneous Procurement Auctions under Oligopoly Aaro Hazak, Tanel Kerikmäe, Evelin Pärn-Lee Aaro Hazak, Professor of Institutional Economics at Tallinn University of Technology, has led several research grant projects and applied studies on the regulatory and broader institutional context of development into knowledge economies and companies’ R&D related decisions. He is leading the Horizon 2020 grant project “Institutions for Knowledge Intensive Development” (IKID, 2017-2020, EUR 1.3 million), which is focused on micro level incentives and macro level institutional mechanisms to encourage and facilitate knowledge creation and absorption. Corresponding author, Department of Economics and Finance, Tallinn University of Technology, Akadeemia tee 3, Tallinn 12618, Estonia; email: aaro.hazak@taltech.ee, telephone: +3726204050 Tanel Kerikmäe is Jean Monnet Professor of European Law and Head of Tallinn Law School at Tallinn University of Technology. He has been active as an expert for public and private institutions and international organizations, and he has been teaching and supervising at several universities worldwide. Tallinn Law School, Tallinn University of Technology, Akadeemia tee 3, Tallinn 12618, Estonia; email: tanel.kerikmae@taltech.ee Evelin Pärn-Lee is Early Stage Researcher and PhD student at Tallinn University of Technology. Her research is related to the interface of competition law and innovation, and competition policy of small states. Apart from academic work, she has over 15 years of international consultancy experience as an attorney at law. Tallinn Law School, Tallinn University of Technology, Akadeemia tee 3, Tallinn 12618, Estonia; email: evelin.parn-lee@taltech.ee Abstract Splitting of large procurements into several smaller ones has been propagated, for example in the European Union and OECD members, as a way for enhancing competition and improving institutional framework for market efficiency. This paper presents a conceptual argumentation on