Integration, particularly economic integration, is high on the policy agenda in Europe – relating to both possible opportunities and potential threats. International economic integration is a complex notion, the definitions are not only often vague but also differing depending on time and place. One could say, it is the elimination of economic ‘barriers’ between two or more economies whereby such barriers can be any boundary or ‘line’ (usually national boundaries) over which the mobilities of goods, services and factors of production factors (capital and labor), as well as communication flows, are hindered or relatively low. To counter such effects – which lower trade and welfare – the goal of economic integration can be followed which includes the removal of discrimination in national economic rules (institutions) and the creation of common policies on both sides of the barrier under joint surveillance leading to more freedom for economic agents on both sides to engage in economic transactions and thus more trade, more competition, more political cooperation, strengthening common interests and a greater incentive to avoid conflict.

European Commission: European Website on Integration

https://ec.europa.eu/migrant-integration/home_en

European Union: History of the EU

https://european-union.europa.eu/principles-countries-history/history-eu_en

Welfens, P.J.J.: An Accidental Brexit

https://link.springer.com/book/10.1007/978-3-319-58271-9

Große Hüttmann, M.: Theorien der europäischen Integration

https://www.bpb.de/kurz-knapp/lexika/das-europalexikon/177303/theorien-der-europaeischen-integration/

Bundeszentrale für politische Bildung: Zu den Ursachen: Europäische ­Integration und Produktivitätswachstum

https://www.bpb.de/kurz-knapp/zahlen-und-fakten/deutschland-in-daten/221466/zu-den-ursachen-europaeische-integration-und-produktivitaetswachstum/