In the information and communication technology (ICT) sector, industry consortia play a critical role in developing compatibility standards that enable interoperability, drive innovation, and shape competitive dynamics. These consortia vary widely in size and composition and are often created to establish de facto standards through market-based coordination. While the literature suggests that structural features, such as the size of the consortium and the diversity of its members, can influence standardisation outcomes, empirical evidence quantifying these effects remains limited. This thesis investigates how the size and industry diversity of ICT consortia affect their success, defined through two key dimensions: the longevity of the consortium and its output productivity in generating technical deliverables. Drawing on theories of network effects, resource pooling, and complementary assets, the study hypothesises that both size and diversity follow an inverted-U shaped relationship with success, offering benefits up to a point, beyond which coordination complexity may reduce effectiveness...