This paper provides an industrial organisation perspective on the economics of data. This literature has focused on ownership and exchange of consumer data, not on business to business data. The novel contributions made are: (i) highlighting the importance of shared data as an input to production; (ii) proposing a framework for analysing how control of data shared between businesses affects competition and market power. The focus is on data as an input to production, a possibility whenever the supply is “contract data based” either involving changes in asset ownership or requiring agreed coordinated performance across multiple businesses. To explore the implications we propose a model of vertical separation, with an ‘upstream’ market for data control and imperfect competition in a ‘downstream’ market for supply of goods/ services. This combines connection costs upstream with a Salop circle downstream. The modelling explores how varying the ownership arrangements for upstream data control impacts on downstream market power, with different outcomes depending on whether the upstream data access is provided competitively, by a for-profit monopoly, a cooperative owned by all downstream firms or by a subset of downstream firms. This highlights the importance of governance of data control for promoting competition in contract data-based goods/services. It also highlights the role of connection costs in data control and the potential for reducing these, through standardisation. The paper discusses the application in several contexts, both financial (payments, securities clearing and settlement, trade finance) and non-financial (logistics and supply chains, registers of land ownership and travel services).