At the same time, practical observation shows that this phenomenon is taking place before formal creation of economic unions.
Economic integration benefits (growth of economy, specifically the GDP; raise of productivity) depend on the level of development as well as a scale of unifying states.
Among the main benefits for the countries which decided to be unified is a free access to markets of the other member states.
A 2005 article by Harald Badinger estimated that the GDP per capita of the European Union would have been approximately 20% lower if no integration had taken place since 1950.
The European Union is often cited as an example of this, as the economic integration of western and central Europe coincided with a period of peace and a reduction in ethno-nationalist sentiment.