The Gulf countries have adopted a unique combination of policies to encourage diversification with largely positive results, while there are significant distinctions between the individual cases. This work evaluates various examples to show the extent to which the Gulf economies have diversifed to date, and how results can be measured, taking into consideration factors such as composition of GDP or exports; government services; and the categorization of industrial activities downstream of resources extraction (oil refining, petrochemicals) and their availability (aluminium, phosphates, iron, steel, glass and other energy- and resource-intensive industries). This work brings together state-of-the-art analysis by international scholars who participated in a major joint initiative by the EU and the GCC, the al-Jisr Gulf-Europe Research Program.